experimental and control group in research

The Importance of Experimental and Control Groups in Research Design

Table of Contents

Have you ever wondered how scientists ensure the treatments or interventions they study actually cause the outcomes they observe? The secret lies in their research design, specifically in the use of experimental and control group s. These groups are the backbone of psychological experiments, and they play a critical role in helping researchers determine the effectiveness of new therapies, the impact of social changes, or the potential benefits of education al programs.

Understanding experimental and control groups

At the heart of any psychological experiment, you’ll find two key components: the experimental group and the control group . The experimental group consists of participants who receive the treatment or experience the manipulation that the researchers are testing. In contrast, the control group does not receive the treatment or experience the manipulation. By comparing these two groups, researchers can isolate the effects of the treatment from other factors that might influence the outcomes.

Why control groups matter

Control groups serve as a benchmark for comparison. Imagine a study exploring the effects of a new educational program on student performance. Without a control group, which continues with the standard curriculum, it would be difficult to conclude whether observed improvements in the experimental group were due to the new program or other variables like maturation, the placebo effect, or even seasonal changes.

The power of random assignment

Random assignment is the process of allocating participants to either the experimental or control group by chance. This method is crucial because it helps balance out any pre-existing differences between group members. For instance, if one group inadvertently had more participants with a natural aptitude for the subject matter, it would skew the results. Random assignment minimizes this risk, leading to more reliable and valid findings.

Controlling for extraneous variables

Extraneous variables are factors other than the independent variable that might affect the dependent variable. These can include participant characteristics, environmental conditions, and researchers’ biases. Effective research design, with well-structured experimental and control groups, helps control these extraneous variables, ensuring that the treatment is the only difference between the groups.

Types of extraneous variables

Different types of extraneous variables can threaten the validity of an experiment. Some common examples include:

• Participant variables: Differences in participants’ age, gender, or background.
• Situational variables: Variations in the environment where the experiment takes place, such as time of day or room temperature.
• Researcher variables: The researcher’s behavior or expectations influencing the results.

Strategies to control extraneous variables

Researchers can use several strategies to control for extraneous variables, such as:

• Standardization: Keeping procedures consistent for all participants.
• Blinding: Preventing participants or researchers from knowing who is in the experimental or control group.
• Matching: Pairing participants in the experimental and control groups based on certain characteristics.

Enhancing validity through comparisons

Validity refers to the accuracy of an experiment’s results. By comparing the experimental group to the control group, researchers can strengthen the validity of their findings. This comparison helps to ensure that the changes observed in the experimental group are indeed due to the treatment and not some other factor.

Internal versus external validity

Internal validity is the degree to which an experiment accurately establishes a cause-and-effect relationship between the treatment and the observed outcome. External validity, on the other hand, is the extent to which the results can be generalized to other settings, populations, or times. Both types of validity are crucial for the overall credibility of the research.

Improving validity with control groups

Control groups help improve both internal and external validity. For internal validity , they provide a baseline to measure the treatment’s effect. For external validity, if the control group is representative of the wider population, the findings are more likely to hold true in real-world settings.

Real-world implications of experimental and control groups

The use of experimental and control groups extends far beyond the laboratory. In the real world, these research designs inform public policy, healthcare decisions, educational reforms, and more. By rigorously testing new interventions against control conditions, researchers can make evidence-based recommendations that have the potential to improve countless lives.

Examples of experimental research in action

Consider the following scenarios where experimental and control groups have made a significant impact:

• Medical trials: Testing new medications or treatments to ensure they are both safe and effective before they are approved for public use.
• Education: Evaluating the effectiveness of new teaching methods or curricula to enhance student learning outcomes.
• Psychology: Investigating the efficacy of different therapeutic approaches for mental health conditions.

Challenges and ethical considerations

While experimental and control groups are powerful tools, they also come with challenges and ethical considerations. Researchers must navigate issues such as participant consent, the potential for harm, and the equitable distribution of the treatment under study.

Experimental and control groups are the cornerstone of rigorous psychological research. They allow scientists to draw meaningful conclusions about cause and effect, control for extraneous variables, and enhance the validity of their findings. As a result, this research design is not just an academic exercise; it has profound implications for our understanding of human behavior and the improvement of society.

What do you think? How might the principles of experimental and control groups be applied to evaluate the effectiveness of decisions in your own life? Can you think of a situation where a control group might have given you clearer insights into the results of your actions?

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Research Methods in Psychology

1 Introduction to Psychological Research – Objectives and Goals, Problems, Hypothesis and Variables

• Nature of Psychological Research
• The Context of Discovery
• Context of Justification
• Characteristics of Psychological Research
• Goals and Objectives of Psychological Research

2 Introduction to Psychological Experiments and Tests

• Independent and Dependent Variables
• Extraneous Variables
• Experimental and Control Groups
• Introduction of Test
• Types of Psychological Test
• Uses of Psychological Tests

3 Steps in Research

• Research Process
• Identification of the Problem
• Review of Literature
• Formulating a Hypothesis
• Identifying Manipulating and Controlling Variables
• Formulating a Research Design
• Constructing Devices for Observation and Measurement
• Sample Selection and Data Collection
• Data Analysis and Interpretation
• Hypothesis Testing
• Drawing Conclusion

4 Types of Research and Methods of Research

• Historical Research
• Descriptive Research
• Correlational Research
• Qualitative Research
• Ex-Post Facto Research
• True Experimental Research
• Quasi-Experimental Research

5 Definition and Description Research Design, Quality of Research Design

• Research Design
• Purpose of Research Design
• Design Selection
• Criteria of Research Design
• Qualities of Research Design

6 Experimental Design (Control Group Design and Two Factor Design)

• Experimental Design
• Control Group Design
• Two Factor Design

7 Survey Design

• Survey Research Designs
• Steps in Survey Design
• Structuring and Designing the Questionnaire
• Interviewing Methodology
• Data Analysis
• Final Report

8 Single Subject Design

• Single Subject Design: Definition and Meaning
• Phases Within Single Subject Design
• Requirements of Single Subject Design
• Characteristics of Single Subject Design
• Types of Single Subject Design
• Advantages of Single Subject Design
• Disadvantages of Single Subject Design

9 Observation Method

• Definition and Meaning of Observation
• Characteristics of Observation
• Types of Observation
• Advantages and Disadvantages of Observation
• Guides for Observation Method

10 Interview and Interviewing

• Definition of Interview
• Types of Interview
• Aspects of Qualitative Research Interviews
• Interview Questions
• Convergent Interviewing as Action Research
• Research Team

11 Questionnaire Method

• Definition and Description of Questionnaires
• Types of Questionnaires
• Purpose of Questionnaire Studies
• Designing Research Questionnaires
• The Methods to Make a Questionnaire Efficient
• The Types of Questionnaire to be Included in the Questionnaire
• Advantages and Disadvantages of Questionnaire
• When to Use a Questionnaire?

12 Case Study

• Definition and Description of Case Study Method
• Historical Account of Case Study Method
• Designing Case Study
• Requirements for Case Studies
• Guideline to Follow in Case Study Method
• Other Important Measures in Case Study Method
• Case Reports

13 Report Writing

• Purpose of a Report
• Writing Style of the Report
• Report Writing – the Do’s and the Don’ts
• Format for Report in Psychology Area
• Major Sections in a Report

14 Review of Literature

• Purposes of Review of Literature
• Sources of Review of Literature
• Types of Literature
• Writing Process of the Review of Literature
• Preparation of Index Card for Reviewing and Abstracting

15 Methodology

• Definition and Purpose of Methodology
• Participants (Sample)
• Apparatus and Materials

16 Result, Analysis and Discussion of the Data

• Definition and Description of Results
• Statistical Presentation
• Tables and Figures

17 Summary and Conclusion

• Summary Definition and Description
• Guidelines for Writing a Summary
• Writing the Summary and Choosing Words
• A Process for Paraphrasing and Summarising
• Summary of a Report
• Writing Conclusions

18 References in Research Report

• Reference List (the Format)
• References (Process of Writing)
• Reference List and Print Sources
• Electronic Sources
• Book on CD Tape and Movie
• Reference Specifications
• General Guidelines to Write References

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control group

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• Verywell Mind - What Is a Control Group?
• National Center for Biotechnology Information - PubMed Central - Control Group Design: Enhancing Rigor in Research of Mind-Body Therapies for Depression

control group , the standard to which comparisons are made in an experiment. Many experiments are designed to include a control group and one or more experimental groups; in fact, some scholars reserve the term experiment for study designs that include a control group. Ideally, the control group and the experimental groups are identical in every way except that the experimental groups are subjected to treatments or interventions believed to have an effect on the outcome of interest while the control group is not. Inclusion of a control group greatly strengthens researchers’ ability to draw conclusions from a study. Indeed, only in the presence of a control group can a researcher determine whether a treatment under investigation truly has a significant effect on an experimental group, and the possibility of making an erroneous conclusion is reduced. See also scientific method .

A typical use of a control group is in an experiment in which the effect of a treatment is unknown and comparisons between the control group and the experimental group are used to measure the effect of the treatment. For instance, in a pharmaceutical study to determine the effectiveness of a new drug on the treatment of migraines , the experimental group will be administered the new drug and the control group will be administered a placebo (a drug that is inert, or assumed to have no effect). Each group is then given the same questionnaire and asked to rate the effectiveness of the drug in relieving symptoms . If the new drug is effective, the experimental group is expected to have a significantly better response to it than the control group. Another possible design is to include several experimental groups, each of which is given a different dosage of the new drug, plus one control group. In this design, the analyst will compare results from each of the experimental groups to the control group. This type of experiment allows the researcher to determine not only if the drug is effective but also the effectiveness of different dosages. In the absence of a control group, the researcher’s ability to draw conclusions about the new drug is greatly weakened, due to the placebo effect and other threats to validity. Comparisons between the experimental groups with different dosages can be made without including a control group, but there is no way to know if any of the dosages of the new drug are more or less effective than the placebo.

It is important that every aspect of the experimental environment be as alike as possible for all subjects in the experiment. If conditions are different for the experimental and control groups, it is impossible to know whether differences between groups are actually due to the difference in treatments or to the difference in environment. For example, in the new migraine drug study, it would be a poor study design to administer the questionnaire to the experimental group in a hospital setting while asking the control group to complete it at home. Such a study could lead to a misleading conclusion, because differences in responses between the experimental and control groups could have been due to the effect of the drug or could have been due to the conditions under which the data were collected. For instance, perhaps the experimental group received better instructions or was more motivated by being in the hospital setting to give accurate responses than the control group.

In non-laboratory and nonclinical experiments, such as field experiments in ecology or economics , even well-designed experiments are subject to numerous and complex variables that cannot always be managed across the control group and experimental groups. Randomization, in which individuals or groups of individuals are randomly assigned to the treatment and control groups, is an important tool to eliminate selection bias and can aid in disentangling the effects of the experimental treatment from other confounding factors. Appropriate sample sizes are also important.

A control group study can be managed in two different ways. In a single-blind study, the researcher will know whether a particular subject is in the control group, but the subject will not know. In a double-blind study , neither the subject nor the researcher will know which treatment the subject is receiving. In many cases, a double-blind study is preferable to a single-blind study, since the researcher cannot inadvertently affect the results or their interpretation by treating a control subject differently from an experimental subject.

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10 Experimental research

Experimental research—often considered to be the ‘gold standard’ in research designs—is one of the most rigorous of all research designs. In this design, one or more independent variables are manipulated by the researcher (as treatments), subjects are randomly assigned to different treatment levels (random assignment), and the results of the treatments on outcomes (dependent variables) are observed. The unique strength of experimental research is its internal validity (causality) due to its ability to link cause and effect through treatment manipulation, while controlling for the spurious effect of extraneous variable.

Experimental research is best suited for explanatory research—rather than for descriptive or exploratory research—where the goal of the study is to examine cause-effect relationships. It also works well for research that involves a relatively limited and well-defined set of independent variables that can either be manipulated or controlled. Experimental research can be conducted in laboratory or field settings. Laboratory experiments , conducted in laboratory (artificial) settings, tend to be high in internal validity, but this comes at the cost of low external validity (generalisability), because the artificial (laboratory) setting in which the study is conducted may not reflect the real world. Field experiments are conducted in field settings such as in a real organisation, and are high in both internal and external validity. But such experiments are relatively rare, because of the difficulties associated with manipulating treatments and controlling for extraneous effects in a field setting.

Experimental research can be grouped into two broad categories: true experimental designs and quasi-experimental designs. Both designs require treatment manipulation, but while true experiments also require random assignment, quasi-experiments do not. Sometimes, we also refer to non-experimental research, which is not really a research design, but an all-inclusive term that includes all types of research that do not employ treatment manipulation or random assignment, such as survey research, observational research, and correlational studies.

Basic concepts

Treatment and control groups. In experimental research, some subjects are administered one or more experimental stimulus called a treatment (the treatment group ) while other subjects are not given such a stimulus (the control group ). The treatment may be considered successful if subjects in the treatment group rate more favourably on outcome variables than control group subjects. Multiple levels of experimental stimulus may be administered, in which case, there may be more than one treatment group. For example, in order to test the effects of a new drug intended to treat a certain medical condition like dementia, if a sample of dementia patients is randomly divided into three groups, with the first group receiving a high dosage of the drug, the second group receiving a low dosage, and the third group receiving a placebo such as a sugar pill (control group), then the first two groups are experimental groups and the third group is a control group. After administering the drug for a period of time, if the condition of the experimental group subjects improved significantly more than the control group subjects, we can say that the drug is effective. We can also compare the conditions of the high and low dosage experimental groups to determine if the high dose is more effective than the low dose.

Treatment manipulation. Treatments are the unique feature of experimental research that sets this design apart from all other research methods. Treatment manipulation helps control for the ‘cause’ in cause-effect relationships. Naturally, the validity of experimental research depends on how well the treatment was manipulated. Treatment manipulation must be checked using pretests and pilot tests prior to the experimental study. Any measurements conducted before the treatment is administered are called pretest measures , while those conducted after the treatment are posttest measures .

Random selection and assignment. Random selection is the process of randomly drawing a sample from a population or a sampling frame. This approach is typically employed in survey research, and ensures that each unit in the population has a positive chance of being selected into the sample. Random assignment, however, is a process of randomly assigning subjects to experimental or control groups. This is a standard practice in true experimental research to ensure that treatment groups are similar (equivalent) to each other and to the control group prior to treatment administration. Random selection is related to sampling, and is therefore more closely related to the external validity (generalisability) of findings. However, random assignment is related to design, and is therefore most related to internal validity. It is possible to have both random selection and random assignment in well-designed experimental research, but quasi-experimental research involves neither random selection nor random assignment.

Threats to internal validity. Although experimental designs are considered more rigorous than other research methods in terms of the internal validity of their inferences (by virtue of their ability to control causes through treatment manipulation), they are not immune to internal validity threats. Some of these threats to internal validity are described below, within the context of a study of the impact of a special remedial math tutoring program for improving the math abilities of high school students.

History threat is the possibility that the observed effects (dependent variables) are caused by extraneous or historical events rather than by the experimental treatment. For instance, students’ post-remedial math score improvement may have been caused by their preparation for a math exam at their school, rather than the remedial math program.

Maturation threat refers to the possibility that observed effects are caused by natural maturation of subjects (e.g., a general improvement in their intellectual ability to understand complex concepts) rather than the experimental treatment.

Testing threat is a threat in pre-post designs where subjects’ posttest responses are conditioned by their pretest responses. For instance, if students remember their answers from the pretest evaluation, they may tend to repeat them in the posttest exam.

Not conducting a pretest can help avoid this threat.

Instrumentation threat , which also occurs in pre-post designs, refers to the possibility that the difference between pretest and posttest scores is not due to the remedial math program, but due to changes in the administered test, such as the posttest having a higher or lower degree of difficulty than the pretest.

Mortality threat refers to the possibility that subjects may be dropping out of the study at differential rates between the treatment and control groups due to a systematic reason, such that the dropouts were mostly students who scored low on the pretest. If the low-performing students drop out, the results of the posttest will be artificially inflated by the preponderance of high-performing students.

Regression threat —also called a regression to the mean—refers to the statistical tendency of a group’s overall performance to regress toward the mean during a posttest rather than in the anticipated direction. For instance, if subjects scored high on a pretest, they will have a tendency to score lower on the posttest (closer to the mean) because their high scores (away from the mean) during the pretest were possibly a statistical aberration. This problem tends to be more prevalent in non-random samples and when the two measures are imperfectly correlated.

Two-group experimental designs

Pretest-posttest control group design . In this design, subjects are randomly assigned to treatment and control groups, subjected to an initial (pretest) measurement of the dependent variables of interest, the treatment group is administered a treatment (representing the independent variable of interest), and the dependent variables measured again (posttest). The notation of this design is shown in Figure 10.1.

Statistical analysis of this design involves a simple analysis of variance (ANOVA) between the treatment and control groups. The pretest-posttest design handles several threats to internal validity, such as maturation, testing, and regression, since these threats can be expected to influence both treatment and control groups in a similar (random) manner. The selection threat is controlled via random assignment. However, additional threats to internal validity may exist. For instance, mortality can be a problem if there are differential dropout rates between the two groups, and the pretest measurement may bias the posttest measurement—especially if the pretest introduces unusual topics or content.

Posttest -only control group design . This design is a simpler version of the pretest-posttest design where pretest measurements are omitted. The design notation is shown in Figure 10.2.

The treatment effect is measured simply as the difference in the posttest scores between the two groups:

The appropriate statistical analysis of this design is also a two-group analysis of variance (ANOVA). The simplicity of this design makes it more attractive than the pretest-posttest design in terms of internal validity. This design controls for maturation, testing, regression, selection, and pretest-posttest interaction, though the mortality threat may continue to exist.

Because the pretest measure is not a measurement of the dependent variable, but rather a covariate, the treatment effect is measured as the difference in the posttest scores between the treatment and control groups as:

Due to the presence of covariates, the right statistical analysis of this design is a two-group analysis of covariance (ANCOVA). This design has all the advantages of posttest-only design, but with internal validity due to the controlling of covariates. Covariance designs can also be extended to pretest-posttest control group design.

Factorial designs

Two-group designs are inadequate if your research requires manipulation of two or more independent variables (treatments). In such cases, you would need four or higher-group designs. Such designs, quite popular in experimental research, are commonly called factorial designs. Each independent variable in this design is called a factor , and each subdivision of a factor is called a level . Factorial designs enable the researcher to examine not only the individual effect of each treatment on the dependent variables (called main effects), but also their joint effect (called interaction effects).

In a factorial design, a main effect is said to exist if the dependent variable shows a significant difference between multiple levels of one factor, at all levels of other factors. No change in the dependent variable across factor levels is the null case (baseline), from which main effects are evaluated. In the above example, you may see a main effect of instructional type, instructional time, or both on learning outcomes. An interaction effect exists when the effect of differences in one factor depends upon the level of a second factor. In our example, if the effect of instructional type on learning outcomes is greater for three hours/week of instructional time than for one and a half hours/week, then we can say that there is an interaction effect between instructional type and instructional time on learning outcomes. Note that the presence of interaction effects dominate and make main effects irrelevant, and it is not meaningful to interpret main effects if interaction effects are significant.

Hybrid experimental designs

Hybrid designs are those that are formed by combining features of more established designs. Three such hybrid designs are randomised bocks design, Solomon four-group design, and switched replications design.

Randomised block design. This is a variation of the posttest-only or pretest-posttest control group design where the subject population can be grouped into relatively homogeneous subgroups (called blocks ) within which the experiment is replicated. For instance, if you want to replicate the same posttest-only design among university students and full-time working professionals (two homogeneous blocks), subjects in both blocks are randomly split between the treatment group (receiving the same treatment) and the control group (see Figure 10.5). The purpose of this design is to reduce the ‘noise’ or variance in data that may be attributable to differences between the blocks so that the actual effect of interest can be detected more accurately.

Solomon four-group design . In this design, the sample is divided into two treatment groups and two control groups. One treatment group and one control group receive the pretest, and the other two groups do not. This design represents a combination of posttest-only and pretest-posttest control group design, and is intended to test for the potential biasing effect of pretest measurement on posttest measures that tends to occur in pretest-posttest designs, but not in posttest-only designs. The design notation is shown in Figure 10.6.

Switched replication design . This is a two-group design implemented in two phases with three waves of measurement. The treatment group in the first phase serves as the control group in the second phase, and the control group in the first phase becomes the treatment group in the second phase, as illustrated in Figure 10.7. In other words, the original design is repeated or replicated temporally with treatment/control roles switched between the two groups. By the end of the study, all participants will have received the treatment either during the first or the second phase. This design is most feasible in organisational contexts where organisational programs (e.g., employee training) are implemented in a phased manner or are repeated at regular intervals.

Quasi-experimental designs

Quasi-experimental designs are almost identical to true experimental designs, but lacking one key ingredient: random assignment. For instance, one entire class section or one organisation is used as the treatment group, while another section of the same class or a different organisation in the same industry is used as the control group. This lack of random assignment potentially results in groups that are non-equivalent, such as one group possessing greater mastery of certain content than the other group, say by virtue of having a better teacher in a previous semester, which introduces the possibility of selection bias . Quasi-experimental designs are therefore inferior to true experimental designs in interval validity due to the presence of a variety of selection related threats such as selection-maturation threat (the treatment and control groups maturing at different rates), selection-history threat (the treatment and control groups being differentially impacted by extraneous or historical events), selection-regression threat (the treatment and control groups regressing toward the mean between pretest and posttest at different rates), selection-instrumentation threat (the treatment and control groups responding differently to the measurement), selection-testing (the treatment and control groups responding differently to the pretest), and selection-mortality (the treatment and control groups demonstrating differential dropout rates). Given these selection threats, it is generally preferable to avoid quasi-experimental designs to the greatest extent possible.

In addition, there are quite a few unique non-equivalent designs without corresponding true experimental design cousins. Some of the more useful of these designs are discussed next.

Regression discontinuity (RD) design . This is a non-equivalent pretest-posttest design where subjects are assigned to the treatment or control group based on a cut-off score on a preprogram measure. For instance, patients who are severely ill may be assigned to a treatment group to test the efficacy of a new drug or treatment protocol and those who are mildly ill are assigned to the control group. In another example, students who are lagging behind on standardised test scores may be selected for a remedial curriculum program intended to improve their performance, while those who score high on such tests are not selected from the remedial program.

Because of the use of a cut-off score, it is possible that the observed results may be a function of the cut-off score rather than the treatment, which introduces a new threat to internal validity. However, using the cut-off score also ensures that limited or costly resources are distributed to people who need them the most, rather than randomly across a population, while simultaneously allowing a quasi-experimental treatment. The control group scores in the RD design do not serve as a benchmark for comparing treatment group scores, given the systematic non-equivalence between the two groups. Rather, if there is no discontinuity between pretest and posttest scores in the control group, but such a discontinuity persists in the treatment group, then this discontinuity is viewed as evidence of the treatment effect.

Proxy pretest design . This design, shown in Figure 10.11, looks very similar to the standard NEGD (pretest-posttest) design, with one critical difference: the pretest score is collected after the treatment is administered. A typical application of this design is when a researcher is brought in to test the efficacy of a program (e.g., an educational program) after the program has already started and pretest data is not available. Under such circumstances, the best option for the researcher is often to use a different prerecorded measure, such as students’ grade point average before the start of the program, as a proxy for pretest data. A variation of the proxy pretest design is to use subjects’ posttest recollection of pretest data, which may be subject to recall bias, but nevertheless may provide a measure of perceived gain or change in the dependent variable.

Separate pretest-posttest samples design . This design is useful if it is not possible to collect pretest and posttest data from the same subjects for some reason. As shown in Figure 10.12, there are four groups in this design, but two groups come from a single non-equivalent group, while the other two groups come from a different non-equivalent group. For instance, say you want to test customer satisfaction with a new online service that is implemented in one city but not in another. In this case, customers in the first city serve as the treatment group and those in the second city constitute the control group. If it is not possible to obtain pretest and posttest measures from the same customers, you can measure customer satisfaction at one point in time, implement the new service program, and measure customer satisfaction (with a different set of customers) after the program is implemented. Customer satisfaction is also measured in the control group at the same times as in the treatment group, but without the new program implementation. The design is not particularly strong, because you cannot examine the changes in any specific customer’s satisfaction score before and after the implementation, but you can only examine average customer satisfaction scores. Despite the lower internal validity, this design may still be a useful way of collecting quasi-experimental data when pretest and posttest data is not available from the same subjects.

An interesting variation of the NEDV design is a pattern-matching NEDV design , which employs multiple outcome variables and a theory that explains how much each variable will be affected by the treatment. The researcher can then examine if the theoretical prediction is matched in actual observations. This pattern-matching technique—based on the degree of correspondence between theoretical and observed patterns—is a powerful way of alleviating internal validity concerns in the original NEDV design.

Perils of experimental research

Experimental research is one of the most difficult of research designs, and should not be taken lightly. This type of research is often best with a multitude of methodological problems. First, though experimental research requires theories for framing hypotheses for testing, much of current experimental research is atheoretical. Without theories, the hypotheses being tested tend to be ad hoc, possibly illogical, and meaningless. Second, many of the measurement instruments used in experimental research are not tested for reliability and validity, and are incomparable across studies. Consequently, results generated using such instruments are also incomparable. Third, often experimental research uses inappropriate research designs, such as irrelevant dependent variables, no interaction effects, no experimental controls, and non-equivalent stimulus across treatment groups. Findings from such studies tend to lack internal validity and are highly suspect. Fourth, the treatments (tasks) used in experimental research may be diverse, incomparable, and inconsistent across studies, and sometimes inappropriate for the subject population. For instance, undergraduate student subjects are often asked to pretend that they are marketing managers and asked to perform a complex budget allocation task in which they have no experience or expertise. The use of such inappropriate tasks, introduces new threats to internal validity (i.e., subject’s performance may be an artefact of the content or difficulty of the task setting), generates findings that are non-interpretable and meaningless, and makes integration of findings across studies impossible.

The design of proper experimental treatments is a very important task in experimental design, because the treatment is the raison d’etre of the experimental method, and must never be rushed or neglected. To design an adequate and appropriate task, researchers should use prevalidated tasks if available, conduct treatment manipulation checks to check for the adequacy of such tasks (by debriefing subjects after performing the assigned task), conduct pilot tests (repeatedly, if necessary), and if in doubt, use tasks that are simple and familiar for the respondent sample rather than tasks that are complex or unfamiliar.

In summary, this chapter introduced key concepts in the experimental design research method and introduced a variety of true experimental and quasi-experimental designs. Although these designs vary widely in internal validity, designs with less internal validity should not be overlooked and may sometimes be useful under specific circumstances and empirical contingencies.

Social Science Research: Principles, Methods and Practices (Revised edition) Copyright © 2019 by Anol Bhattacherjee is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Experimental Group in Psychology Experiments

In a randomized and controlled psychology experiment , the researchers are examining the impact of an experimental condition on a group of participants (does the independent variable 'X' cause a change in the dependent variable 'Y'?). To determine cause and effect, there must be at least two groups to compare, the experimental group and the control group.

The participants who are in the experimental condition are those who receive the treatment or intervention of interest. The data from their outcomes are collected and compared to the data from a group that did not receive the experimental treatment. The control group may have received no treatment at all, or they may have received a placebo treatment or the standard treatment in current practice.

Comparing the experimental group to the control group allows researchers to see how much of an impact the intervention had on the participants.

A Closer Look at Experimental Groups

Imagine that you want to do an experiment to determine if listening to music while working out can lead to greater weight loss. After getting together a group of participants, you randomly assign them to one of three groups. One group listens to upbeat music while working out, one group listens to relaxing music, and the third group listens to no music at all. All of the participants work out for the same amount of time and the same number of days each week.

In this experiment, the group of participants listening to no music while working out is the control group. They serve as a baseline with which to compare the performance of the other two groups. The other two groups in the experiment are the experimental groups.   They each receive some level of the independent variable, which in this case is listening to music while working out.

In this experiment, you find that the participants who listened to upbeat music experienced the greatest weight loss result, largely because those who listened to this type of music exercised with greater intensity than those in the other two groups. By comparing the results from your experimental groups with the results of the control group, you can more clearly see the impact of the independent variable.  

Some Things to Know

When it comes to using experimental groups in a psychology experiment, there are a few important things to know:

• In order to determine the impact of an independent variable, it is important to have at least two different treatment conditions. This usually involves using a control group that receives no treatment against an experimental group that receives the treatment. However, there can also be a number of different experimental groups in the same experiment.
• Care must be taken when assigning participants to groups. So how do researchers determine who is in the control group and who is in the experimental group? In an ideal situation, the researchers would use random assignment to place participants in groups. In random assignment, each individual stands an equal shot at being assigned to either group. Participants might be randomly assigned using methods such as a coin flip or a number draw. By using random assignment, researchers can help ensure that the groups are not unfairly stacked with people who share characteristics that might unfairly skew the results.
• Variables must be well-defined. Before you begin manipulating things in an experiment, you need to have very clear operational definitions in place. These definitions clearly explain what your variables are, including exactly how you are manipulating the independent variable and exactly how you are measuring the outcomes.

A Word From Verywell

Experiments play an important role in the research process and allow psychologists to investigate cause-and-effect relationships between different variables. Having one or more experimental groups allows researchers to vary different levels or types of the experimental variable and then compare the effects of these changes against a control group. The goal of this experimental manipulation is to gain a better understanding of the different factors that may have an impact on how people think, feel, and act.

Byrd-Bredbenner C, Wu F, Spaccarotella K, Quick V, Martin-Biggers J, Zhang Y. Systematic review of control groups in nutrition education intervention research . Int J Behav Nutr Phys Act. 2017;14(1):91. doi:10.1186/s12966-017-0546-3

Steingrimsdottir HS, Arntzen E. On the utility of within-participant research design when working with patients with neurocognitive disorders . Clin Interv Aging. 2015;10:1189-1200. doi:10.2147/CIA.S81868

Oberste M, Hartig P, Bloch W, et al. Control group paradigms in studies investigating acute effects of exercise on cognitive performance—An experiment on expectation-driven placebo effects . Front Hum Neurosci. 2017;11:600. doi:10.3389/fnhum.2017.00600

Kim H. Statistical notes for clinical researchers: Analysis of covariance (ANCOVA) . Restor Dent Endod . 2018;43(4):e43. doi:10.5395/rde.2018.43.e43

Bate S, Karp NA. A common control group — Optimising the experiment design to maximise sensitivity . PLoS ONE. 2014;9(12):e114872. doi:10.1371/journal.pone.0114872

Myers A, Hansen C. Experimental Psychology . 7th Ed. Cengage Learning; 2012.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Understanding Control Groups for Research

Introduction

What are control groups in research, examples of control groups in research, control group vs. experimental group, types of control groups, control groups in non-experimental research.

A control group is typically thought of as the baseline in an experiment. In an experiment, clinical trial, or other sort of controlled study, there are at least two groups whose results are compared against each other.

The experimental group receives some sort of treatment, and their results are compared against those of the control group, which is not given the treatment. This is important to determine whether there is an identifiable causal relationship between the treatment and the resulting effects.

As intuitive as this may sound, there is an entire methodology that is useful to understanding the role of the control group in experimental research and as part of a broader concept in research. This article will examine the particulars of that methodology so you can design your research more rigorously .

Suppose that a friend or colleague of yours has a headache. You give them some over-the-counter medicine to relieve some of the pain. Shortly after they take the medicine, the pain is gone and they feel better. In casual settings, we can assume that it must be the medicine that was the cause of their headache going away.

In scientific research, however, we don't really know if the medicine made a difference or if the headache would have gone away on its own. Maybe in the time it took for the headache to go away, they ate or drank something that might have had an effect. Perhaps they had a quick nap that helped relieve the tension from the headache. Without rigorously exploring this phenomenon , any number of confounding factors exist that can make us question the actual efficacy of any particular treatment.

Experimental research relies on observing differences between the two groups by "controlling" the independent variable , or in the case of our example above, the medicine that is given or not given depending on the group. The dependent variable in this case is the change in how the person suffering the headache feels, and the difference between taking and not taking the medicine is evidence (or lack thereof) that the treatment is effective.

The catch is that, between the control group and other groups (typically called experimental groups), it's important to ensure that all other factors are the same or at least as similar as possible. Things such as age, fitness level, and even occupation can affect the likelihood someone has a headache and whether a certain medication is effective.

Faced with this dynamic, researchers try to make sure that participants in their control group and experimental group are as similar as possible to each other, with the only difference being the treatment they receive.

Experimental research is often associated with scientists in lab coats holding beakers containing liquids with funny colors. Clinical trials that deal with medical treatments rely primarily, if not exclusively, on experimental research designs involving comparisons between control and experimental groups.

However, many studies in the social sciences also employ some sort of experimental design which calls for the use of control groups. This type of research is useful when researchers are trying to confirm or challenge an existing notion or measure the difference in effects.

Workplace efficiency research

How might a company know if an employee training program is effective? They may decide to pilot the program to a small group of their employees before they implement the training to their entire workforce.

If they adopt an experimental design, they could compare results between an experimental group of workers who participate in the training program against a control group who continues as per usual without any additional training.

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Mental health research

Music certainly has profound effects on psychology, but what kind of music would be most effective for concentration? Here, a researcher might be interested in having participants in a control group perform a series of tasks in an environment with no background music, and participants in multiple experimental groups perform those same tasks with background music of different genres. The subsequent analysis could determine how well people perform with classical music, jazz music, or no music at all in the background.

Educational research

Suppose that you want to improve reading ability among elementary school students, and there is research on a particular teaching method that is associated with facilitating reading comprehension. How do you measure the effects of that teaching method?

A study could be conducted on two groups of otherwise equally proficient students to measure the difference in test scores. The teacher delivers the same instruction to the control group as they have to previous students, but they teach the experimental group using the new technique. A reading test after a certain amount of instruction could determine the extent of effectiveness of the new teaching method.

As you can see from the three examples above, experimental groups are the counterbalance to control groups. A control group offers an essential point of comparison. For an experimental study to be considered credible, it must establish a baseline against which novel research is conducted.

Researchers can determine the makeup of their experimental and control groups from their literature review . Remember that the objective of a review is to establish what is known about the object of inquiry and what is not known. Where experimental groups explore the unknown aspects of scientific knowledge, a control group is a sort of simulation of what would happen if the treatment or intervention was not administered. As a result, it will benefit researchers to have a foundational knowledge of the existing research to create a credible control group against which experimental results are compared, especially in terms of remaining sensitive to relevant participant characteristics that could confound the effects of your treatment or intervention so that you can appropriately distribute participants between the experimental and control groups.

There are multiple control groups to consider depending on the study you are looking to conduct. All of them are variations of the basic control group used to establish a baseline for experimental conditions.

No-treatment control group

This kind of control group is common when trying to establish the effects of an experimental treatment against the absence of treatment. This is arguably the most straightforward approach to an experimental design as it aims to directly demonstrate how a certain change in conditions produces an effect.

Placebo control group

In this case, the control group receives some sort of treatment under the exact same procedures as those in the experimental group. The only difference in this case is that the treatment in the placebo control group has already been judged to be ineffective, except that the research participants don't know that it is ineffective.

Placebo control groups (or negative control groups) are useful for allowing researchers to account for any psychological or affective factors that might impact the outcomes. The negative control group exists to explicitly eliminate factors other than changes in the independent variable conditions as causes of the effects experienced in the experimental group.

Positive control group

Contrasted with a no-treatment control group, a positive control group employs a treatment against which the treatment in the experimental group is compared. However, unlike in a placebo group, participants in a positive control group receive treatment that is known to have an effect.

If we were to use our first example of headache medicine, a researcher could compare results between medication that is commonly known as effective against the newer medication that the researcher thinks is more effective. Positive control groups are useful for validating experimental results when compared against familiar results.

Historical control group

Rather than study participants in control group conditions, researchers may employ existing data to create historical control groups. This form of control group is useful for examining changing conditions over time, particularly when incorporating past conditions that can't be replicated in the analysis.

Qualitative research more often relies on non-experimental research such as observations and interviews to examine phenomena in their natural environments. This sort of research is more suited for inductive and exploratory inquiries, not confirmatory studies meant to test or measure a phenomenon.

That said, the broader concept of a control group is still present in observational and interview research in the form of a comparison group. Comparison groups are used in qualitative research designs to show differences between phenomena, with the exception being that there is no baseline against which data is analyzed.

Comparison groups are useful when an experimental environment cannot produce results that would be applicable to real-world conditions. Research inquiries examining the social world face challenges of having too many variables to control, making observations and interviews across comparable groups more appropriate for data collection than clinical or sterile environments.

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Controlled Experiment

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Editor-in-Chief for Simply Psychology

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This is when a hypothesis is scientifically tested.

In a controlled experiment, an independent variable (the cause) is systematically manipulated, and the dependent variable (the effect) is measured; any extraneous variables are controlled.

The researcher can operationalize (i.e., define) the studied variables so they can be objectively measured. The quantitative data can be analyzed to see if there is a difference between the experimental and control groups.

What is the control group?

In experiments scientists compare a control group and an experimental group that are identical in all respects, except for one difference – experimental manipulation.

Unlike the experimental group, the control group is not exposed to the independent variable under investigation and so provides a baseline against which any changes in the experimental group can be compared.

Since experimental manipulation is the only difference between the experimental and control groups, we can be sure that any differences between the two are due to experimental manipulation rather than chance.

Randomly allocating participants to independent variable groups means that all participants should have an equal chance of participating in each condition.

The principle of random allocation is to avoid bias in how the experiment is carried out and limit the effects of participant variables.

What are extraneous variables?

The researcher wants to ensure that the manipulation of the independent variable has changed the changes in the dependent variable.

Hence, all the other variables that could affect the dependent variable to change must be controlled. These other variables are called extraneous or confounding variables.

Extraneous variables should be controlled were possible, as they might be important enough to provide alternative explanations for the effects.

In practice, it would be difficult to control all the variables in a child’s educational achievement. For example, it would be difficult to control variables that have happened in the past.

A researcher can only control the current environment of participants, such as time of day and noise levels.

Why conduct controlled experiments?

Scientists use controlled experiments because they allow for precise control of extraneous and independent variables. This allows a cause-and-effect relationship to be established.

Controlled experiments also follow a standardized step-by-step procedure. This makes it easy for another researcher to replicate the study.

Key Terminology

Experimental group.

The group being treated or otherwise manipulated for the sake of the experiment.

Control Group

They receive no treatment and are used as a comparison group.

Ecological validity

The degree to which an investigation represents real-life experiences.

Experimenter effects

These are the ways that the experimenter can accidentally influence the participant through their appearance or behavior.

Demand characteristics

The clues in an experiment lead the participants to think they know what the researcher is looking for (e.g., the experimenter’s body language).

Independent variable (IV)

The variable the experimenter manipulates (i.e., changes) – is assumed to have a direct effect on the dependent variable.

Dependent variable (DV)

Variable the experimenter measures. This is the outcome (i.e., the result) of a study.

Extraneous variables (EV)

All variables that are not independent variables but could affect the results (DV) of the experiment. Extraneous variables should be controlled where possible.

Confounding variables

Variable(s) that have affected the results (DV), apart from the IV. A confounding variable could be an extraneous variable that has not been controlled.

Random Allocation

Randomly allocating participants to independent variable conditions means that all participants should have an equal chance of participating in each condition.

Order effects

Changes in participants’ performance due to their repeating the same or similar test more than once. Examples of order effects include:

(i) practice effect: an improvement in performance on a task due to repetition, for example, because of familiarity with the task;

(ii) fatigue effect: a decrease in performance of a task due to repetition, for example, because of boredom or tiredness.

What is the control in an experiment?

In an experiment , the control is a standard or baseline group not exposed to the experimental treatment or manipulation. It serves as a comparison group to the experimental group, which does receive the treatment or manipulation.

The control group helps to account for other variables that might influence the outcome, allowing researchers to attribute differences in results more confidently to the experimental treatment.

Establishing a cause-and-effect relationship between the manipulated variable (independent variable) and the outcome (dependent variable) is critical in establishing a cause-and-effect relationship between the manipulated variable.

What is the purpose of controlling the environment when testing a hypothesis?

Controlling the environment when testing a hypothesis aims to eliminate or minimize the influence of extraneous variables. These variables other than the independent variable might affect the dependent variable, potentially confounding the results.

By controlling the environment, researchers can ensure that any observed changes in the dependent variable are likely due to the manipulation of the independent variable, not other factors.

This enhances the experiment’s validity, allowing for more accurate conclusions about cause-and-effect relationships.

It also improves the experiment’s replicability, meaning other researchers can repeat the experiment under the same conditions to verify the results.

Why are hypotheses important to controlled experiments?

Hypotheses are crucial to controlled experiments because they provide a clear focus and direction for the research. A hypothesis is a testable prediction about the relationship between variables.

It guides the design of the experiment, including what variables to manipulate (independent variables) and what outcomes to measure (dependent variables).

The experiment is then conducted to test the validity of the hypothesis. If the results align with the hypothesis, they provide evidence supporting it.

The hypothesis may be revised or rejected if the results do not align. Thus, hypotheses are central to the scientific method, driving the iterative inquiry, experimentation, and knowledge advancement process.

What is the experimental method?

The experimental method is a systematic approach in scientific research where an independent variable is manipulated to observe its effect on a dependent variable, under controlled conditions.

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Control Group Definition and Examples

The control group is the set of subjects that does not receive the treatment in a study. In other words, it is the group where the independent variable is held constant. This is important because the control group is a baseline for measuring the effects of a treatment in an experiment or study. A controlled experiment is one which includes one or more control groups.

• The experimental group experiences a treatment or change in the independent variable. In contrast, the independent variable is constant in the control group.
• A control group is important because it allows meaningful comparison. The researcher compares the experimental group to it to assess whether or not there is a relationship between the independent and dependent variable and the magnitude of the effect.
• There are different types of control groups. A controlled experiment has one more control group.

Control Group vs Experimental Group

The only difference between the control group and experimental group is that subjects in the experimental group receive the treatment being studied, while participants in the control group do not. Otherwise, all other variables between the two groups are the same.

Control Group vs Control Variable

A control group is not the same thing as a control variable. A control variable or controlled variable is any factor that is held constant during an experiment. Examples of common control variables include temperature, duration, and sample size. The control variables are the same for both the control and experimental groups.

Types of Control Groups

There are different types of control groups:

• Placebo group : A placebo group receives a placebo , which is a fake treatment that resembles the treatment in every respect except for the active ingredient. Both the placebo and treatment may contain inactive ingredients that produce side effects. Without a placebo group, these effects might be attributed to the treatment.
• Positive control group : A positive control group has conditions that guarantee a positive test result. The positive control group demonstrates an experiment is capable of producing a positive result. Positive controls help researchers identify problems with an experiment.
• Negative control group : A negative control group consists of subjects that are not exposed to a treatment. For example, in an experiment looking at the effect of fertilizer on plant growth, the negative control group receives no fertilizer.
• Natural control group : A natural control group usually is a set of subjects who naturally differ from the experimental group. For example, if you compare the effects of a treatment on women who have had children, the natural control group includes women who have not had children. Non-smokers are a natural control group in comparison to smokers.
• Randomized control group : The subjects in a randomized control group are randomly selected from a larger pool of subjects. Often, subjects are randomly assigned to either the control or experimental group. Randomization reduces bias in an experiment. There are different methods of randomly assigning test subjects.

Control Group Examples

Here are some examples of different control groups in action:

Negative Control and Placebo Group

For example, consider a study of a new cancer drug. The experimental group receives the drug. The placebo group receives a placebo, which contains the same ingredients as the drug formulation, minus the active ingredient. The negative control group receives no treatment. The reason for including the negative group is because the placebo group experiences some level of placebo effect, which is a response to experiencing some form of false treatment.

Positive and Negative Controls

For example, consider an experiment looking at whether a new drug kills bacteria. The experimental group exposes bacterial cultures to the drug. If the group survives, the drug is ineffective. If the group dies, the drug is effective.

The positive control group has a culture of bacteria that carry a drug resistance gene. If the bacteria survive drug exposure (as intended), then it shows the growth medium and conditions allow bacterial growth. If the positive control group dies, it indicates a problem with the experimental conditions. A negative control group of bacteria lacking drug resistance should die. If the negative control group survives, something is wrong with the experimental conditions.

• Bailey, R. A. (2008).  Design of Comparative Experiments . Cambridge University Press. ISBN 978-0-521-68357-9.
• Chaplin, S. (2006). “The placebo response: an important part of treatment”.  Prescriber . 17 (5): 16–22. doi: 10.1002/psb.344
• Hinkelmann, Klaus; Kempthorne, Oscar (2008).  Design and Analysis of Experiments, Volume I: Introduction to Experimental Design  (2nd ed.). Wiley. ISBN 978-0-471-72756-9.
• Pithon, M.M. (2013). “Importance of the control group in scientific research.” Dental Press J Orthod . 18 (6):13-14. doi: 10.1590/s2176-94512013000600003
• Stigler, Stephen M. (1992). “A Historical View of Statistical Concepts in Psychology and Educational Research”. American Journal of Education . 101 (1): 60–70. doi: 10.1086/444032

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What are Controlled Experiments?

Determining Cause and Effect

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A controlled experiment is a highly focused way of collecting data and is especially useful for determining patterns of cause and effect. This type of experiment is used in a wide variety of fields, including medical, psychological, and sociological research. Below, we’ll define what controlled experiments are and provide some examples.

Key Takeaways: Controlled Experiments

• A controlled experiment is a research study in which participants are randomly assigned to experimental and control groups.
• A controlled experiment allows researchers to determine cause and effect between variables.
• One drawback of controlled experiments is that they lack external validity (which means their results may not generalize to real-world settings).

Experimental and Control Groups

To conduct a controlled experiment , two groups are needed: an experimental group and a control group . The experimental group is a group of individuals that are exposed to the factor being examined. The control group, on the other hand, is not exposed to the factor. It is imperative that all other external influences are held constant . That is, every other factor or influence in the situation needs to remain exactly the same between the experimental group and the control group. The only thing that is different between the two groups is the factor being researched.

For example, if you were studying the effects of taking naps on test performance, you could assign participants to two groups: participants in one group would be asked to take a nap before their test, and those in the other group would be asked to stay awake. You would want to ensure that everything else about the groups (the demeanor of the study staff, the environment of the testing room, etc.) would be equivalent for each group. Researchers can also develop more complex study designs with more than two groups. For example, they might compare test performance among participants who had a 2-hour nap, participants who had a 20-minute nap, and participants who didn’t nap.

Assigning Participants to Groups

In controlled experiments, researchers use  random assignment (i.e. participants are randomly assigned to be in the experimental group or the control group) in order to minimize potential confounding variables in the study. For example, imagine a study of a new drug in which all of the female participants were assigned to the experimental group and all of the male participants were assigned to the control group. In this case, the researchers couldn’t be sure if the study results were due to the drug being effective or due to gender—in this case, gender would be a confounding variable.

Random assignment is done in order to ensure that participants are not assigned to experimental groups in a way that could bias the study results. A study that compares two groups but does not randomly assign participants to the groups is referred to as quasi-experimental, rather than a true experiment.

Blind and Double-Blind Studies

In a blind experiment, participants don’t know whether they are in the experimental or control group. For example, in a study of a new experimental drug, participants in the control group may be given a pill (known as a placebo ) that has no active ingredients but looks just like the experimental drug. In a double-blind study , neither the participants nor the experimenter knows which group the participant is in (instead, someone else on the research staff is responsible for keeping track of group assignments). Double-blind studies prevent the researcher from inadvertently introducing sources of bias into the data collected.

Example of a Controlled Experiment

If you were interested in studying whether or not violent television programming causes aggressive behavior in children, you could conduct a controlled experiment to investigate. In such a study, the dependent variable would be the children’s behavior, while the independent variable would be exposure to violent programming. To conduct the experiment, you would expose an experimental group of children to a movie containing a lot of violence, such as martial arts or gun fighting. The control group, on the other hand, would watch a movie that contained no violence.

To test the aggressiveness of the children, you would take two measurements : one pre-test measurement made before the movies are shown, and one post-test measurement made after the movies are watched. Pre-test and post-test measurements should be taken of both the control group and the experimental group. You would then use statistical techniques to determine whether the experimental group showed a significantly greater increase in aggression, compared to participants in the control group.

Studies of this sort have been done many times and they usually find that children who watch a violent movie are more aggressive afterward than those who watch a movie containing no violence.

Strengths and Weaknesses

Controlled experiments have both strengths and weaknesses. Among the strengths is the fact that results can establish causation. That is, they can determine cause and effect between variables. In the above example, one could conclude that being exposed to representations of violence causes an increase in aggressive behavior. This kind of experiment can also zero-in on a single independent variable, since all other factors in the experiment are held constant.

On the downside, controlled experiments can be artificial. That is, they are done, for the most part, in a manufactured laboratory setting and therefore tend to eliminate many real-life effects. As a result, analysis of a controlled experiment must include judgments about how much the artificial setting has affected the results. Results from the example given might be different if, say, the children studied had a conversation about the violence they watched with a respected adult authority figure, like a parent or teacher, before their behavior was measured. Because of this, controlled experiments can sometimes have lower external validity (that is, their results might not generalize to real-world settings).

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Control Group: The Key Elements In Experimental Research

Understand the design and interpretation of control group in research experiments for powerful conclusions

The control group constitutes a baseline for comparison, enabling researchers to assess the true effects of independent variables. Researchers can effectively assess the impact of independent variables and discern causation from correlation, by comparing the results of experimental groups to those of control groups. This article will highlight the significance and implementation of control groups in research experiments, and explain their role in ensuring scientific methodology and reliable findings. We will explore the fundamental principles of control groups, examine their types, and discuss their importance in minimizing biases and confounding factors.

What Is A Control Group?

A control group is a fundamental component of scientific experiments designed to compare and evaluate the effects of an intervention or treatment. It serves as a baseline against which the experimental group is measured. The control group consists of individuals or subjects who do not receive the experimental treatment but are otherwise subjected to the same conditions and procedures as the experimental group. Working with a control group, researchers can assess the specific impact of the intervention by comparing the outcomes between the experimental and control groups.

Related article: The Role Of Experimental Groups In Research

The Role Of A Control Group In Scientific Experiments

A control group plays a crucial role in scientific experiments as it enables researchers to establish a valid cause-and-effect relationship between the experimental treatment and the observed outcomes. By comparing the experimental group’s results with those of the control group, researchers can determine whether any observed effects are due to the treatment or other factors. The control group serves as a standard for comparison, helping to isolate the specific influence of the intervention being tested. It provides a baseline against which experimental group outcomes can be evaluated and allows researchers to draw accurate conclusions about the treatment’s efficacy or the impact of other variables being studied.

Why Is A Control Group Necessary?

Including a control group in scientific experiments is essential for ensuring the reliability and validity of the findings. Without a control group, it becomes challenging to determine whether any observed changes or effects are truly attributable to the intervention or simply a result of chance or other factors. The control group allows researchers to differentiate between the effects of the experimental treatment and background noise or confounding variables because it provides a reference point. A well-designed control group is crucial for generating reliable and meaningful results, intensifying the scientific rigor of the study, and supporting evidence-based decision-making in various fields of research.

Types Of Control Groups

In scientific experiments, different types of control groups are used to ensure accurate and meaningful results. These control groups help researchers compare the effects of an intervention or treatment against a reference point. Four common types of control groups are negative controls, positive controls, placebo controls, and randomized control groups.

Negative Controls

Negative controls are an integral part of scientific experiments, serving as a reference to establish the absence of a specific effect. In these control groups, no treatment is administered, allowing researchers to compare the outcomes with the experimental group. Researchers can identify and account for confounding variables and background effects that may influence the results when they include negative control groups. This ensures the specificity of the treatment and enhances the validity of the study. Negative controls can take various forms, such as placebos or control groups receiving no treatment, depending on the research question.

Positive controls

Positive controls are references to validate the reliability and sensitivity of the experimental setup. In these control groups, a known treatment or condition is applied to generate an expected response or outcome. By including positive controls, researchers can assess whether the experimental conditions and methodology are capable of detecting the desired effect. Positive controls act as a benchmark, providing evidence that the experimental system is functioning properly and capable of producing the anticipated results. This helps researchers ensure the validity and accuracy of their findings by confirming that the experimental conditions are conducive to detecting the intended response.

Placebo controls

Placebo controls play a significant role in medical and clinical research by providing a baseline for comparison and evaluating the effectiveness of a new treatment or intervention. In a placebo control group, participants receive an inactive substance or sham procedure that is indistinguishable from the active treatment being tested. The purpose of the placebo control is to assess the specific effects of the treatment by comparing it to the effects observed in the placebo group. By administering a placebo, researchers can account for the psychological and physiological responses that may occur simply due to the participants’ belief in receiving treatment. This helps determine the true efficacy of the active treatment, as any observed improvements in the treatment group can be attributed to the treatment itself, beyond the placebo effect. Placebo controls are essential in clinical trials and other studies to minimize bias, establish the true therapeutic benefits of treatment, and ensure the reliability of the results.

Randomized Control Group

Randomized control groups are an essential component of research studies as they introduce unpredictability to control factors. By randomly assigning participants to either the control or treatment group, researchers ensure that the variables not specifically tested are evenly distributed. This randomization helps eliminate bias and allows for accurate analysis of the independent variable. By using randomized control groups, researchers can draw reliable conclusions about the impact of the variables being studied. 

Quasi-Experimental Designs And Their Role In Social Policy Studies

Quasi-experimental designs in social policy studies often utilize control groups to assess the impact of interventions or policies on a target population. While these designs do not involve random assignment of participants to groups, they still incorporate a control group to establish a baseline for comparison. The control group consists of individuals who do not receive the intervention or policy being studied, allowing researchers to evaluate the effects of the intervention by comparing outcomes between the treatment group and the control group. This helps control for confounding variables and provides insights into a causal relationship between the intervention and the observed outcomes. 

Implementing Control Groups In Experimental Design And Analysis

Control groups serve as a reference point against which the effects of experimental interventions can be measured. They provide a baseline to compare with the treatment group, allowing researchers to determine the true impact of the variables under investigation. This approach helps establish causal relationships and increases the internal validity of the research. 

Randomized Controlled Experiments (RCTs) For Public Policy Studies

Randomized controlled experiments are widely used in public policy studies. RCTs involve randomly assigning participants to either a treatment group or a control group. The treatment group receives the intervention or policy being tested, while the control group does not. RCTs help ensure that any observed differences between the groups are not due to pre-existing factors, increasing the reliability of the study’s findings. RCTs are particularly valuable in evaluating the impact of public policies and interventions on a large scale.

Non-Experimental Research Vs. Actual Experimentation

When determining the baseline for comparison in research, researchers must consider whether to use non-experimental research or actual experimentation. Non-experimental research involves observing and analyzing existing data without manipulating any variables. This approach is helpful in situations where it is not feasible or ethical to conduct an experiment. On the other hand, actual experimentation involves actively manipulating variables and comparing groups with and without the intervention. While actual experimentation provides stronger causal evidence, non-experimental research can still provide valuable insights when experiments are not possible.

Identifying Confounding Variables And Factors

Confounding variables and factors are extraneous variables that can influence the relationship between the independent and dependent variables in a study. Identifying and controlling for confounding variables is crucial to ensure accurate and valid results. Researchers employ various techniques to address confounding variables, such as random assignment of participants to groups, matching participants based on relevant characteristics, or statistical techniques like regression analysis. By accounting for confounding variables, researchers can strengthen the internal validity of their studies and draw more accurate conclusions about the relationship between variables.

The Vital Role Of The Control Group In Scientific Methodology And Analysis

In experimental studies, the control group serves as a standard against which the effects of a particular intervention or treatment are measured. By keeping all variables constant except for the one being studied, researchers can isolate the true impact of the intervention. This helps to establish causality and determine whether the observed effects are indeed due to the intervention or simply a result of other factors.

In addition to experimental studies, control groups are also essential in observational and epidemiological research. They help researchers account for potential biases and confounding factors when analyzing the relationship between variables. By comparing a group exposed to a certain risk factor or condition with a similar group that is not exposed, researchers can better understand the true impact of the risk factor or condition on the outcome of interest.

Overall, the control group serves as a guide in scientific methodology and analysis. It allows researchers to draw valid and reliable conclusions, enhance the internal validity of their studies, and provide more robust evidence for decision-making in various fields, including medicine, psychology, biology, and social sciences.

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Statistics By Jim

Making statistics intuitive

Control Group in an Experiment

By Jim Frost 3 Comments

A control group in an experiment does not receive the treatment. Instead, it serves as a comparison group for the treatments. Researchers compare the results of a treatment group to the control group to determine the effect size, also known as the treatment effect.

Imagine that a treatment group receives a vaccine and it has an infection rate of 10%. By itself, you don’t know if that’s an improvement. However, if you also have an unvaccinated control group with an infection rate of 20%, you know the vaccine improved the outcome by 10 percentage points.

By serving as a basis for comparison, the control group reveals the treatment’s effect.

Related post : Effect Sizes in Statistics

Using Control Groups in Experiments

Most experiments include a control group and at least one treatment group. In an ideal experiment, the subjects in all groups start with the same overall characteristics except that those in the treatment groups receive a treatment. When the groups are otherwise equivalent before treatment begins, you can attribute differences after the experiment to the treatments.

Randomized controlled trials (RCTs) assign subjects to the treatment and control groups randomly. This process helps ensure the groups are comparable when treatment begins. Consequently, treatment effects are the most likely cause for differences between groups at the end of the study. Statisticians consider RCTs to be the gold standard. To learn more about this process, read my post, Random Assignment in Experiments .

Observational studies either can’t use randomized groups or don’t use them because they’re too costly or problematic. In these studies, the characteristics of the control group might be different from the treatment groups at the start of the study, making it difficult to estimate the treatment effect accurately at the end. Case-Control studies are a specific type of observational study that uses a control group.

For these types of studies, analytical methods and design choices, such as regression analysis and matching, can help statistically mitigate confounding variables. Matching involves selecting participants with similar characteristics. For each participant in the treatment group, the researchers find a subject with comparable traits to include in the control group. To learn more about this type of study and matching, read my post, Observational Studies Explained .

Control groups are key way to increase the internal validity of an experiment. To learn more, read my post about internal and external validity .

Randomized versus non-randomized control groups are just several of the different types you can have. We’ll look at more kinds later!

Related posts : When to Use Regression Analysis

Example of a Control Group

Suppose we want to determine whether regular vitamin consumption affects the risk of dying. Our experiment has the following two experimental groups:

• Control group : Does not consume vitamin supplements
• Treatment group : Regularly consumes vitamin supplements.

In this experiment, we randomly assign subjects to the two groups. Because we use random assignment, the two groups start with similar characteristics, including healthy habits, physical attributes, medical conditions, and other factors affecting the outcome. The intentional introduction of vitamin supplements in the treatment group is the only systematic difference between the groups.

After the experiment is complete, we compare the death risk between the treatment and control groups. Because the groups started roughly equal, we can reasonably attribute differences in death risk at the end of the study to vitamin consumption. By having the control group as the basis of comparison, the effect of vitamin consumption becomes clear!

Types of Control Groups

Researchers can use different types of control groups in their experiments. Earlier, you learned about the random versus non-random kinds, but there are other variations. You can use various types depending on your research goals, constraints, and ethical issues, among other things.

Negative Control Group

The group introduces a condition that the researchers expect won’t have an effect. This group typically receives no treatment. These experiments compare the effectiveness of the experimental treatment to no treatment. For example, in a vaccine study, a negative control group does not get the vaccine.

Positive Control Group

Positive control groups typically receive a standard treatment that science has already proven effective. These groups serve as a benchmark for the performance of a conventional treatment. In this vein, experiments with positive control groups compare the effectiveness of a new treatment to a standard one.

For example, an old blood pressure medicine can be the treatment in a positive control group, while the treatment group receives the new, experimental blood pressure medicine. The researchers want to determine whether the new treatment is better than the previous treatment.

In these studies, subjects can still take the standard medication for their condition, a potentially critical ethics issue.

Placebo Control Group

Placebo control groups introduce a treatment lookalike that will not affect the outcome. Standard examples of placebos are sugar pills and saline solution injections instead of genuine medicine. The key is that the placebo looks like the actual treatment. Researchers use this approach when the recipients’ belief that they’re receiving the treatment might influence their outcomes. By using placebos, the experiment controls for these psychological benefits. The researchers want to determine whether the treatment performs better than the placebo effect.

Learn more about the Placebo Effect .

Blinded Control Groups

If the subject’s awareness of their group assignment might affect their outcomes, the researchers can use a blinded experimental design that does not tell participants their group membership. Typically, blinded control groups will receive placebos, as described above. In a double-blinded control group, both subjects and researchers don’t know group assignments.

Waitlist Control Group

When there is a waitlist to receive a new treatment, those on the waitlist can serve as a control group until they receive treatment. This type of design avoids ethical concerns about withholding a better treatment until the study finishes. This design can be a variation of a positive control group because the subjects might be using conventional medicines while on the waitlist.

Historical Control Group

When historical data for a comparison group exists, it can serve as a control group for an experiment. The group doesn’t exist in the study, but the researchers compare the treatment group to the existing data. For example, the researchers might have infection rate data for unvaccinated individuals to compare to the infection rate among the vaccinated participants in their study. This approach allows everyone in the experiment to receive the new treatment. However, differences in place, time, and other circumstances can reduce the value of these comparisons. In other words, other factors might account for the apparent effects.

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Reader Interactions

December 19, 2021 at 9:17 am

Thank you very much Jim for your quick and comprehensive feedback. Extremely helpful!! Regards, Arthur

December 17, 2021 at 4:46 pm

Thank you very much Jim, very interesting article.

Can I select a control group at the end of intervention/experiment? Currently I am managing a project in rural Cambodia in five villages, however I did not select any comparison/control site at the beginning. Since I know there are other villages which have not been exposed to any type of intervention, can i select them as a control site during my end-line data collection or it will not be a legitimate control? Thank you very much, Arthur

December 18, 2021 at 1:51 am

You might be able to use that approach, but it’s not ideal. The ideal is to have control groups defined at the beginning of the study. You can use the untreated villages as a type of historical control groups that I talk about in this article. Or, if they’re awaiting to receive the intervention, it might be akin to a waitlist control group.

If you go that route, you’ll need to consider whether there was some systematic reason why these villages have not received any intervention. For example, are the villages in question more remote? And, if there is a systematic reason, would that affect your outcome variable? More generally, are they systematically different? How well do the untreated villages represent your target population?

If you had selected control villages at the beginning, you’d have been better able to ensure there weren’t any systematic differences between the villages receiving interventions and those that didn’t.

If the villages that didn’t receive any interventions are systematically different, you’ll need to incorporate that into your interpretation of the results. Are they different in ways that affect the outcomes you’re measuring? Can those differences account for the difference in outcomes between the treated and untreated villages? Hopefully, you’d be able to measure those differences between untreated/treated villages.

So, yes, you can use that approach. It’s not perfect and there will potentially be more things for you to consider and factor into your conclusions. Despite these drawbacks, it’s possible that using a pseudo control group like that is better than not doing that because at least you can make comparisons to something. Otherwise, you won’t know whether the outcomes in the intervention villages represent an improvement! Just be aware of the extra considerations!

Best of luck with your research!

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• Control Groups and Treatment Groups | Uses & Examples

Control Groups & Treatment Groups | Uses & Examples

Published on 6 May 2022 by Lauren Thomas . Revised on 13 April 2023.

In a scientific study, a control group is used to establish a cause-and-effect relationship by isolating the effect of an independent variable .

Researchers change the independent variable in the treatment group and keep it constant in the control group. Then they compare the results of these groups.

Using a control group means that any change in the dependent variable can be attributed to the independent variable.

Table of contents

Control groups in experiments, control groups in non-experimental research, importance of control groups, frequently asked questions about control groups.

Control groups are essential to experimental design . When researchers are interested in the impact of a new treatment, they randomly divide their study participants into at least two groups:

• The treatment group (also called the experimental group ) receives the treatment whose effect the researcher is interested in.
• The control group receives either no treatment, a standard treatment whose effect is already known, or a placebo (a fake treatment).

The treatment is any independent variable manipulated by the experimenters, and its exact form depends on the type of research being performed. In a medical trial, it might be a new drug or therapy. In public policy studies, it could be a new social policy that some receive and not others.

In a well-designed experiment, all variables apart from the treatment should be kept constant between the two groups. This means researchers can correctly measure the entire effect of the treatment without interference from confounding variables .

• You pay the students in the treatment group for achieving high grades.
• Students in the control group do not receive any money.

Studies can also include more than one treatment or control group. Researchers might want to examine the impact of multiple treatments at once, or compare a new treatment to several alternatives currently available.

• The treatment group gets the new pill.
• Control group 1 gets an identical-looking sugar pill (a placebo).
• Control group 2 gets a pill already approved to treat high blood pressure.

Since the only variable that differs between the three groups is the type of pill, any differences in average blood pressure between the three groups can be credited to the type of pill they received.

• The difference between the treatment group and control group 1 demonstrates the effectiveness of the pill as compared to no treatment.
• The difference between the treatment group and control group 2 shows whether the new pill improves on treatments already available on the market.

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Although control groups are more common in experimental research, they can be used in other types of research too. Researchers generally rely on non-experimental control groups in two cases: quasi-experimental or matching design.

Control groups in quasi-experimental design

While true experiments rely on random assignment to the treatment or control groups, quasi-experimental design uses some criterion other than randomisation to assign people.

Often, these assignments are not controlled by researchers, but are pre-existing groups that have received different treatments. For example, researchers could study the effects of a new teaching method that was applied in some classes in a school but not others, or study the impact of a new policy that is implemented in one region but not in the neighbouring region.

In these cases, the classes that did not use the new teaching method, or the region that did not implement the new policy, is the control group.

Control groups in matching design

In correlational research , matching represents a potential alternate option when you cannot use either true or quasi-experimental designs.

In matching designs, the researcher matches individuals who received the ‘treatment’, or independent variable under study, to others who did not – the control group.

Each member of the treatment group thus has a counterpart in the control group identical in every way possible outside of the treatment. This ensures that the treatment is the only source of potential differences in outcomes between the two groups.

Control groups help ensure the internal validity of your research. You might see a difference over time in your dependent variable in your treatment group. However, without a control group, it is difficult to know whether the change has arisen from the treatment. It is possible that the change is due to some other variables.

If you use a control group that is identical in every other way to the treatment group, you know that the treatment – the only difference between the two groups – must be what has caused the change.

For example, people often recover from illnesses or injuries over time regardless of whether they’ve received effective treatment or not. Thus, without a control group, it’s difficult to determine whether improvements in medical conditions come from a treatment or just the natural progression of time.

Risks from invalid control groups

If your control group differs from the treatment group in ways that you haven’t accounted for, your results may reflect the interference of confounding variables instead of your independent variable.

Minimising this risk

A few methods can aid you in minimising the risk from invalid control groups.

• Ensure that all potential confounding variables are accounted for , preferably through an experimental design if possible, since it is difficult to control for all the possible confounders outside of an experimental environment.
• Use double-blinding . This will prevent the members of each group from modifying their behavior based on whether they were placed in the treatment or control group, which could then lead to biased outcomes.
• Randomly assign your subjects into control and treatment groups. This method will allow you to not only minimise the differences between the two groups on confounding variables that you can directly observe, but also those you cannot.

An experimental group, also known as a treatment group, receives the treatment whose effect researchers wish to study, whereas a control group does not. They should be identical in all other ways.

A true experiment (aka a controlled experiment) always includes at least one control group that doesn’t receive the experimental treatment.

However, some experiments use a within-subjects design to test treatments without a control group. In these designs, you usually compare one group’s outcomes before and after a treatment (instead of comparing outcomes between different groups).

For strong internal validity , it’s usually best to include a control group if possible. Without a control group, it’s harder to be certain that the outcome was caused by the experimental treatment and not by other variables.

In a controlled experiment , all extraneous variables are held constant so that they can’t influence the results. Controlled experiments require:

• A control group that receives a standard treatment, a fake treatment, or no treatment
• Random assignment of participants to ensure the groups are equivalent

Depending on your study topic, there are various other methods of controlling variables .

A confounding variable , also called a confounder or confounding factor, is a third variable in a study examining a potential cause-and-effect relationship.

A confounding variable is related to both the supposed cause and the supposed effect of the study. It can be difficult to separate the true effect of the independent variable from the effect of the confounding variable.

In your research design , it’s important to identify potential confounding variables and plan how you will reduce their impact.

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Considerations of Control Groups: Comparing Active-Control with No Treatment for Examining the Effects of Brief Intervention

Andrew m. lane.

1 Research Centre for Sport, Physical Activity (SPARC) School of Sport, Faculty of Education, Health and Wellbeing, Walsall Campus, University of Wolverhampton, Walsall WS1 3BD, UK; [email protected]

Chris J. Beedie

2 School of Psychology, Canterbury Campus, University of Kent, Canterbury CT2 7NP, UK; [email protected]

Tracey J. Devonport

Andrew p. friesen.

3 Department of Kinesiology, Berks Campus, Pennsylvania State University, Berks, PA 19610, USA; ude.usp@617fxa

Associated Data

The data is not yet publicly available.

Background: A large-scale online study completed by this research team found that brief psychological interventions were associated with high-intensity pleasant emotions and predicted performance. The present study extends this work using data from participants ( n = 3376) who completed all self-report data and engaged in a performance task but who did not engage with an intervention or control condition and therefore present as an opportunistic no-treatment group. Methods: 41,720 participants were selected from the process and outcome focus goals intervention groups, which were the successful interventions ( n = 30,096), active-control ( n = 3039), and no-treatment ( n = 8585). Participants completed a competitive task four times: first as practice, second to establish a baseline, third following an opportunity to complete a brief psychological skills intervention, and lastly following an opportunity to repeat the intervention. Repeated measures MANOVA indicated that over four performance rounds, the intensity of positive emotions increased, performance improved, and the amount of effort participants exerted increased; however, these increases were significantly smaller in the no-treatment group. Conclusions: Findings suggest that not engaging in active training conditions had negative effects. We suggest that these findings have implications for the development and deployment of online interventions.

1. Introduction

The effectiveness of psychological skills such as imagery, goal-setting, and self-talk has been demonstrated in many areas of application [ 1 ], including sport [ 2 ], surgery [ 3 ], and computer gaming [ 4 ]. A recent large-scale study of 44,742 participants found support for the utility of following brief online active psychological skills training to aid emotion regulation and improve performance in a competitive task [ 5 ]. The aforementioned study [ 5 ] tested the effects of three psychological skills: (a) imagery, (b) self-talk, and (c) if–then planning, with each skill directed to one of four different foci: (a) outcome goal, (b) process goal, (c) instruction, or (d) arousal control, resulting in 12 different techniques. A 13th group labelled as a control group received a repetition of instructions on how to perform the task from Olympic gold-medallist Michael Johnson. The argument for labelling these participants as a control group was that they received no active training. They [ 5 ] compared the extent to which performance in the 12 intervention conditions improved over four rounds against the control group. The results illustrated the benefits of engaging in active psychological skills training, and the control group significantly improved also. Interestingly, the control group showed greater improvement in performance, felt more energetic, and exerted more mental effort than participants following instructional interventions.

A key aspect of this study [ 5 ] was the method used to produce the active control group which is used to form the case for the present study. In their study, participants were informed that they would learn about sport psychology and receive personalized feedback from Michael Johnson. Specifically, control group participants were informed, “You have played the game now. You have to find the numbers and finding them can be challenging. It’s a different grid but the challenges will be similar. Spend some time getting mentally ready. Give yourself about 90 seconds to prepare before you start the next round”. Although not receiving specific instructions, the control group received encouragement to perform again from former Olympian Michael Johnson, and encouragement is motivational [ 6 ].

A control group should seek to control the positive beliefs of using the intervention, a point that drives blind and double-blind placebo groups. The control condition should elicit some of the symptoms of the intervention but not those that are in the active treatment (e.g., decaffeinated coffee, a treatment that tastes like coffee, and so could have the active ingredient, but actually does not). In sport psychology interventions these typically involve active training, and as such it is difficult to have a traditional control group.

The present study extends this work [ 5 ] using previously unreported data from the same experiment. The investigators [ 5 ] found many participants engaged in all the performance tests but did not engage with the interventions. These unused data represent a novel condition and offers opportunistic no-treatment control data against the active control and active-training groups used in the previous study [ 5 ]. We hypothesized that the “no-treatment” group would perform significantly worse than the “active-training” and “active-control” groups reported previously [ 5 ].

2. Materials and Methods

2.1. participants.

Participants were 74,204 volunteers who provided informed consent and were recruited to the study via the British Broadcasting Corporation (BBC) Lab UK ( M age = 34.66 years, SD = 14.13). The project was advertised on national television and radio as an online experiment investigating performing under pressure. Participants originated from 103 different countries covering all continents. In the present study, we selected 41,720 ( M age = 34.34, SD = 13.93) participants from the process and outcome focus goals interventions, which were the successful interventions ( n = 30,096; M age = 34.64, SD = 14.07), active-control ( n = 3039, M age = 31.50, SD = 13.41), and no-treatment ( n = 8585, M age = 34.35, SD = 13.93).

2.2. Measures

The study uses the same measures reported previously [ 5 ] and so these are described only briefly here.

2.2.1. Emotion

The items to measure, “Happy”, “Anxious”, “Dejected”, “Angry”, and “Excited”, were used from the same-named factors in the Sport Emotion Questionnaire (SEQ) [ 7 ] and two items “Fatigued” and “Energetic” were included to reflect arousal [ 8 ]. Each item was rated on a 7-point Likert scale (1 = not at all to 7 = extremely) . A single measure of emotion was used so that a high score was indicative of pleasant emotion. Alpha coefficients for emotion at each completion were: Baseline α = 0.72, Round 1 α = 0.70, Round 2 α = 0.68, and Round 3 α = 0.70.

2.2.2. Concentration Game Task

A cognitive task was developed to allow the capture of a large dataset via an online method. The concentration grid task required participants to find and click on numbers in sequence from 1 to 36 as quickly as possible from a 6 × 6 grid. Numbers were presented in a randomised order within the grid, and as such participants had to concentrate and scan the grid to locate and click on the correct number. Participants completed a practice round, where participants performed alone and not against a competitor. Based on practice round results, an artificial computer opponent was introduced to create a sense of competition. The computer opponent was matched against the participant’s grid completion time from the practice round. The participant’s performance was measured by the number of seconds required to complete the grid.

2.2.3. Mental Effort

The Rating Scale of Mental Effort [ 9 ] is a single item scale that was used to assess mental effort (0 = no effort to 150 = complete effort).

2.2.4. Procedure

Data were collected online via the BBC Lab UK website. Participants completed informed consent forms before proceeding to the start of the online experiment. Videos guided participants through the completion of self-report scales and the concentration task. The online programme was narrated by Michael Johnson. Random allocation to experimental treatment groups was completed automatically by an online programme based on demographic data provided by participants. All participants completed the concentration game task before group allocation to provide a baseline measure of performance that could be used to assess whether the groups had pre-existing differences. Participants then rated their mental effort immediately following performance.

An opportunistic no-treatment group ( n = 8595) emerged which consisted of participants who chose not to view the allocated intervention or encouragement video (i.e., active-control group). Instead, these participants immediately proceeded to a second completion of the concentration grid. Further, this was their decision. Therefore, considerations that arise when positive treatment is denied to a subsection of the sample in a randomised control design are not applicable. This no-treatment group is closer to a traditional control group. However, a key difference is that participants were not randomly allocated.

2.2.5. Data Analysis

A repeated measures multivariate analysis of variance examining emotions, effort exerted and performance over the 4 rounds of practice, baseline, the implementation of the intervention, and finally, a repeat of the same intervention. The rationale for the data analysis strategy was to run as few tests as possible. With such a large sample size, it is easy to show significant results even though the size of the effect was low. In the present study, the focus is on significant interaction effects as they show that changes in data vary between groups.

Repeated MANOVA results revealed a significant intervention effect (Wilks lambda 18,83522 = 0.98, p < 0.0001, partial eta 2 = 0.10), a main effect for changes over time (Wilks lambda 9,41769 = 0.74, p < 0.0001, partial eta 2 = 0.26) and a main effect for active-training, active-control, and no-treatment (Wilks lambda 18,83522 = 0.98, p < 0.0001, partial eta 2 = 0.11).

Univariate results indicated that emotions became significantly more positive ( F   6,125304 = 1328.56, p < 0.0001, partial eta 2 = 0.03) following the completion of the intervention (see Figure 1 ). The pattern of significant differences showed that the active-training group benefited the most, followed by the active-control group, with the least benefits being found for the no-treatment group. Weaker significant interaction effects were found for effort invested in performance over rounds of competition ( F   6,125304 = 12.46, p < 0.0001, partial eta 2 = 0.01, see Figure 2 ) and for improvements in performance ( F   6,125304 = 6.42 p < 0.0001, partial eta 2 = 0.001, see Figure 3 ).

Emotion by Competition Rounds, by Active-Training, Active-Control, and No-Treatment.

Effort by Competition Round, by Active-Training, Active-control, and No-Treatment.

Performance by Competition Round, by Active-Training, Active-Control, and No-Treatment.

Results show that there were main effects for time ( F   3,120856 = 1328.56, p = <0.001, partial eta 2 = 0.007) with emotions became significantly more positive ( F 3,1328.56 = 2132.93, p < 0.0001, partial eta 2 = 0.49), performance improving ( F   3,120856 = 1249.97, p = <0.001, partial eta 2 = 0.007) and effort invested ( F   3,120856 = 4836.33, p = <0.001, partial eta 2 = 0.104).

4. Discussion

The present study examined the effects of brief online interventions in comparison to a no-treatment group [ 5 ]. The large sample of data in the active-training and active-control groups offer a good opportunity to conduct a comprehensive examination. A total of 8585 participants did not complete the interventions but engaged fully in other parts of the experiment and therefore represent what typically looks like a non-treatment group. The key difference between these participants and a traditional control group was they were not randomly allocated. Participants in the no-treatment group showed performance improvement from baseline, increased intensity of positive emotions, and increased effort. This result is interpreted as suggesting participants in the no-treatment group were motivated to improve performance, and therefore resemble participants who sign up with a desire to improve performance. However, the rate of change between rounds was slower for the no-treatment group than the active-training and active-control groups, suggesting the active part of either control or training was influential. Compliance with participation protocols is a key factor when examining the effectiveness of interventions. In research, participants who do not comply with protocols is an issue. In real world settings, poor participant compliance minimizes the effectiveness of treatments ranging from COVID-19 vaccines to physical and mental health interventions.

Results demonstrated that the no-treatment group performed significantly worse, made less progress, and reported less optimal psychological states than the active-control and active-treatment groups. These results are not entirely unexpected but exploring possible reasons why they occurred and learning from using online interventions where naturally occurring no-treatment groups could emerge could have useful implications for future work. Positive benefits from participants receiving treatment could be explained by enhanced beliefs that the treatment would work, an effect normally described as a placebo effect. Controlling beliefs is typically achieved by using a blind placebo approach. However, this is not possible where an intervention requires the person to act consciously on information provided. A blind placebo arguably works much better in studies such as caffeine where people still participate in the treatment, believing they are taking the caffeine, but the active ingredients are removed. In such research, great care is made to make a placebo look like an authentic treatment. In a sport psychology intervention where a practitioner teaches the use of psychological skills, there is a requirement for the participant to be active in the process. An active-control group [ 5 ] is one in which basic instructions are repeated and so attempts to control for belief effects. The present study which used a no-treatment group offers the opportunity to compare the effects of active treatments against no-treatment. A no-treatment group resembles what happens in real life when people wish to pick up a skill and learn by trial and error and without specific guidance.

The active-control group benefited from participation in the study more than the no-treatment group. Receiving a message from an inspirational figure such as Michael Johnson and expecting personalised feedback can be argued to provide encouragement, which is motivating [ 6 ]. Whilst encouragement is a simple technique to use as an intervention, it is possible that the effectiveness of it in this context derives from it being delivered by a highly influential figure in sport. This raises the issue of the relative influence of the person who delivers the intervention as an active ingredient. Models of social influence from social psychology have highlighted the importance of the perceived status of the influencer [ 10 ]; however, this issue is under-examined within the context of conducting psychology research. We suggest future research compares the effectiveness of encouragement when the same message is given by different people, with a hypothesis that the more credible the persuader, the more influential it would be.

The current study can also inform future research that uses online methods to investigate psychology interventions. Online data collection that allows people to volitionally skip through the intervention creates naturally occurring control conditions where participants do not expect the intervention to work. In the present study, the no-treatment group was an opportunistic group that emerged once data had been collected and so differed from a traditional control group for whom the condition was randomised.

The present study offers a valuable contribution to knowledge in this area. Results show the value of online research which offers scalability and via data capture processes can facilitate the examination of points of engagement with the task and intervention being delivered. However, we recognise at least two limitations. The first limitation is that we did not obtain feedback from participants that measured any learning effects having completed the intervention. That is, we did not check to see if the knowledge gained was internalised before starting the task. The second limitation is that participants were not randomly allocated into the no-treatment group. We should not see engagement and disengagement as dichotomous concepts and appreciate that the intensity with which people engage with the intervention will vary. A limitation with online studies is that the conditions in which a person learns an intervention and takes a test has many unknown features. We suggest that future research focus on the learning process in terms of what intervention content is retained.

In conclusion, the BBC Lab UK data show the benefits of capturing all keyboard data. The present study used data that were not used previously [ 5 ]. On initial analysis these data were seen as incomplete; however, this shows the benefits of reflecting on what insights such data might provide. We encourage researchers to focus on using entire datasets to interrogate the issue of compliance in completing interventions, and to investigate why non-compliance occurs.

Author Contributions

Conceptualization, A.M.L. and T.J.D.; data collection, A.M.L. and T.J.D.; writing—original draft preparation, A.M.L., C.J.B., T.J.D. and A.P.F.; writing—review and editing, A.M.L., C.J.B., T.J.D. and A.P.F. All authors have read and agreed to the published version of the manuscript.

This Research received no funding.

Institutional Review Board Statement

The study was approved by the Ethics Committee of the University of Wolverhampton (15.02.12).

Informed Consent Statement

Informed consent was obtained from all participants involved in the study.

Data Availability Statement

Conflicts of interest.

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Experimental vs control group: differences explained.

Home » Experimental vs control group: differences explained

Group Comparison Analysis is essential for understanding the differences between experimental and control groups in research. To illustrate, imagine a new medication tested against a placebo. The experimental group receives the medication, while the control group receives no treatment. This setup allows researchers to determine the medication's effectiveness based on the observed outcomes across both groups.

In essence, the experimental group experiences the intervention directly, enabling examination of its impacts. Conversely, the control group serves as a baseline, helping to identify any changes unrelated to the intervention. By analyzing these group differences, researchers gain valuable insights, enhancing the validity and reliability of their conclusions.

Understanding the Basics of Experimental Group Comparison Analysis

Understanding Group Comparison Analysis is essential for anyone interested in experimental research. This analytical approach allows researchers to determine the effects of different conditions on a specific outcome. Typically, this involves dividing participants into an experimental group, which receives the treatment, and a control group, which does not. By comparing the results from these groups, researchers can establish a causal relationship between the intervention and the outcomes.

There are key elements to consider in Group Comparison Analysis. First, the selection of participants must be randomized to eliminate bias. Second, the variables measured must be consistent and reliable to ensure accurate results. Finally, statistical methods are employed to analyze the data, providing a clearer understanding of any differences observed. Focusing on these fundamental aspects can significantly enhance the reliability of experimental findings, contributing to informed decision-making in various fields.

Definition and Purpose of Experimental Groups

Experimental groups are essential elements in the scientific method, particularly in research involving group comparison analysis. Defined simply, an experimental group is a set of individuals or samples subjected to a treatment or condition that is being tested. This allows researchers to observe the effects of the treatment and ascertain its effectiveness compared to other groups. Understanding this concept helps clarify how different variables influence outcomes, enabling better insights into the research subject.

The purpose of having experimental groups lies in their ability to generate reliable data that can be analyzed for meaningful conclusions. By comparing the results from the experimental group with control groups, researchers can identify causal relationships and assess the impact of specific interventions. This structured comparison is crucial for drawing accurate conclusions that guide future improvements, product development, or policy adjustments. Ultimately, experimental groups play a foundational role in advancing knowledge and understanding in various fields.

Definition and Purpose of Control Groups

Control groups are essential in experimental design, serving as the baseline for comparison. They do not receive the experimental treatment, allowing researchers to isolate the effects of the variable being tested. By maintaining consistency across conditions, control groups enable reliable group comparison analysis. This structured approach helps identify whether observed changes in the experimental group result from the treatment applied or other factors.

The purpose of control groups is to minimize bias and ensure valid results. When researchers analyze data, having a control group makes it easier to attribute differences to the independent variable. This distinction is crucial, especially in fields like psychology or medicine, where the impact of interventions can significantly influence outcomes. Understanding the role and purpose of control groups deepens comprehension of experimental results and strengthens the foundation of scientific inquiry.

Key Differences in Group Comparison Analysis

In group comparison analysis, distinguishing between experimental and control groups is essential. The experimental group receives the treatment or intervention being tested, allowing researchers to assess its effectiveness. Conversely, the control group serves as a baseline, remaining untouched by the experimental manipulation. This contrast helps isolate the effects of the intervention from other variables.

Additionally, group comparison analysis considers how random assignment to each group impacts study integrity. Randomization reduces bias, ensuring that results reflect the intervention's true impact rather than pre-existing differences. Furthermore, the measurement of outcomes in both groups is crucial for accurate analysis. Understanding these key differences allows researchers to draw reliable conclusions and make informed decisions based on the findings, enhancing the overall validity of their studies.

Design and Structure Differences

In any Group Comparison Analysis, the design and structure of experimental and control groups play a crucial role. Experimental groups receive the treatment or intervention being tested, while control groups do not, serving as a benchmark for comparison. This fundamental distinction allows researchers to assess the effects of a treatment effectively.

The methodological differences further extend to random assignment and blinding techniques. Random assignment ensures that participants are allocated to groups by chance, reducing bias and enhancing the validity of results. Blinding, whether single or double, minimizes participant and researcher expectations that could influence outcomes. Together, these elements contribute to the integrity of the research, ensuring that observed effects can be linked distinctly to the intervention rather than other variables. Understanding these design and structure differences is vital for interpreting results and drawing meaningful conclusions from the research.

Outcome Measurement and Analysis

In any experimental study, outcome measurement and analysis are crucial for understanding the differences between experimental and control groups. Group Comparison Analysis plays a vital role in evaluating the effectiveness of interventions. This process begins with identifying key metrics, such as time efficiency and quality of insights derived from participant data. It is essential to consider how these factors vary between the groups, allowing researchers to draw meaningful conclusions.

Furthermore, assessing qualitative aspects, such as participant engagement and thematic patterns, can provide deeper insight into the findings. This holistic approach ensures that variations within and across participants are explored. Trends and similarities can uncover common themes, allowing for a clearer understanding of underlying factors driving results. Ultimately, effective outcome measurement and analysis guide decisions based on empirical evidence, ensuring the reliability and validity of the study’s conclusions.

Conclusion: Summarizing Group Comparison Analysis Insights

In summary, the comparison between experimental and control groups yields valuable insights into the effectiveness of interventions. Group Comparison Analysis enables researchers to discern patterns and relationships that form the foundation for informed decisions. As shown in various studies, the experimental group often demonstrates significant differences in outcomes compared to the control group, illustrating the impact of specific variables.

Reflecting on the findings, it is crucial to appreciate the nuances in data interpretation. Understanding these differences not only enhances our methodologies but also paves the way for future research. Through careful analysis, we can transform theoretical insights into practical applications that advance our understanding of behavior and effectiveness in real-world scenarios.

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• Random Assignment in Experiments | Introduction & Examples

Random Assignment in Experiments | Introduction & Examples

Published on March 8, 2021 by Pritha Bhandari . Revised on June 22, 2023.

In experimental research, random assignment is a way of placing participants from your sample into different treatment groups using randomization.

With simple random assignment, every member of the sample has a known or equal chance of being placed in a control group or an experimental group. Studies that use simple random assignment are also called completely randomized designs .

Random assignment is a key part of experimental design . It helps you ensure that all groups are comparable at the start of a study: any differences between them are due to random factors, not research biases like sampling bias or selection bias .

Table of contents

Why does random assignment matter, random sampling vs random assignment, how do you use random assignment, when is random assignment not used, other interesting articles, frequently asked questions about random assignment.

Random assignment is an important part of control in experimental research, because it helps strengthen the internal validity of an experiment and avoid biases.

In experiments, researchers manipulate an independent variable to assess its effect on a dependent variable, while controlling for other variables. To do so, they often use different levels of an independent variable for different groups of participants.

This is called a between-groups or independent measures design.

You use three groups of participants that are each given a different level of the independent variable:

• a control group that’s given a placebo (no dosage, to control for a placebo effect ),
• an experimental group that’s given a low dosage,
• a second experimental group that’s given a high dosage.

Random assignment to helps you make sure that the treatment groups don’t differ in systematic ways at the start of the experiment, as this can seriously affect (and even invalidate) your work.

If you don’t use random assignment, you may not be able to rule out alternative explanations for your results.

• participants recruited from cafes are placed in the control group ,
• participants recruited from local community centers are placed in the low dosage experimental group,
• participants recruited from gyms are placed in the high dosage group.

With this type of assignment, it’s hard to tell whether the participant characteristics are the same across all groups at the start of the study. Gym-users may tend to engage in more healthy behaviors than people who frequent cafes or community centers, and this would introduce a healthy user bias in your study.

Although random assignment helps even out baseline differences between groups, it doesn’t always make them completely equivalent. There may still be extraneous variables that differ between groups, and there will always be some group differences that arise from chance.

Most of the time, the random variation between groups is low, and, therefore, it’s acceptable for further analysis. This is especially true when you have a large sample. In general, you should always use random assignment in experiments when it is ethically possible and makes sense for your study topic.

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Random sampling and random assignment are both important concepts in research, but it’s important to understand the difference between them.

Random sampling (also called probability sampling or random selection) is a way of selecting members of a population to be included in your study. In contrast, random assignment is a way of sorting the sample participants into control and experimental groups.

While random sampling is used in many types of studies, random assignment is only used in between-subjects experimental designs.

Some studies use both random sampling and random assignment, while others use only one or the other.

Random sampling enhances the external validity or generalizability of your results, because it helps ensure that your sample is unbiased and representative of the whole population. This allows you to make stronger statistical inferences .

You use a simple random sample to collect data. Because you have access to the whole population (all employees), you can assign all 8000 employees a number and use a random number generator to select 300 employees. These 300 employees are your full sample.

Random assignment enhances the internal validity of the study, because it ensures that there are no systematic differences between the participants in each group. This helps you conclude that the outcomes can be attributed to the independent variable .

• a control group that receives no intervention.
• an experimental group that has a remote team-building intervention every week for a month.

You use random assignment to place participants into the control or experimental group. To do so, you take your list of participants and assign each participant a number. Again, you use a random number generator to place each participant in one of the two groups.

To use simple random assignment, you start by giving every member of the sample a unique number. Then, you can use computer programs or manual methods to randomly assign each participant to a group.

• Random number generator: Use a computer program to generate random numbers from the list for each group.
• Lottery method: Place all numbers individually in a hat or a bucket, and draw numbers at random for each group.
• Flip a coin: When you only have two groups, for each number on the list, flip a coin to decide if they’ll be in the control or the experimental group.
• Use a dice: When you have three groups, for each number on the list, roll a dice to decide which of the groups they will be in. For example, assume that rolling 1 or 2 lands them in a control group; 3 or 4 in an experimental group; and 5 or 6 in a second control or experimental group.

This type of random assignment is the most powerful method of placing participants in conditions, because each individual has an equal chance of being placed in any one of your treatment groups.

Random assignment in block designs

In more complicated experimental designs, random assignment is only used after participants are grouped into blocks based on some characteristic (e.g., test score or demographic variable). These groupings mean that you need a larger sample to achieve high statistical power .

For example, a randomized block design involves placing participants into blocks based on a shared characteristic (e.g., college students versus graduates), and then using random assignment within each block to assign participants to every treatment condition. This helps you assess whether the characteristic affects the outcomes of your treatment.

In an experimental matched design , you use blocking and then match up individual participants from each block based on specific characteristics. Within each matched pair or group, you randomly assign each participant to one of the conditions in the experiment and compare their outcomes.

Sometimes, it’s not relevant or ethical to use simple random assignment, so groups are assigned in a different way.

When comparing different groups

Sometimes, differences between participants are the main focus of a study, for example, when comparing men and women or people with and without health conditions. Participants are not randomly assigned to different groups, but instead assigned based on their characteristics.

In this type of study, the characteristic of interest (e.g., gender) is an independent variable, and the groups differ based on the different levels (e.g., men, women, etc.). All participants are tested the same way, and then their group-level outcomes are compared.

When it’s not ethically permissible

When studying unhealthy or dangerous behaviors, it’s not possible to use random assignment. For example, if you’re studying heavy drinkers and social drinkers, it’s unethical to randomly assign participants to one of the two groups and ask them to drink large amounts of alcohol for your experiment.

When you can’t assign participants to groups, you can also conduct a quasi-experimental study . In a quasi-experiment, you study the outcomes of pre-existing groups who receive treatments that you may not have any control over (e.g., heavy drinkers and social drinkers). These groups aren’t randomly assigned, but may be considered comparable when some other variables (e.g., age or socioeconomic status) are controlled for.

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If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

• Student’s  t -distribution
• Normal distribution
• Null and Alternative Hypotheses
• Chi square tests
• Confidence interval
• Quartiles & Quantiles
• Cluster sampling
• Stratified sampling
• Data cleansing
• Reproducibility vs Replicability
• Peer review
• Prospective cohort study

Research bias

• Implicit bias
• Cognitive bias
• Placebo effect
• Hawthorne effect
• Hindsight bias
• Affect heuristic
• Social desirability bias

In experimental research, random assignment is a way of placing participants from your sample into different groups using randomization. With this method, every member of the sample has a known or equal chance of being placed in a control group or an experimental group.

Random selection, or random sampling , is a way of selecting members of a population for your study’s sample.

In contrast, random assignment is a way of sorting the sample into control and experimental groups.

Random sampling enhances the external validity or generalizability of your results, while random assignment improves the internal validity of your study.

Random assignment is used in experiments with a between-groups or independent measures design. In this research design, there’s usually a control group and one or more experimental groups. Random assignment helps ensure that the groups are comparable.

In general, you should always use random assignment in this type of experimental design when it is ethically possible and makes sense for your study topic.

To implement random assignment , assign a unique number to every member of your study’s sample .

Then, you can use a random number generator or a lottery method to randomly assign each number to a control or experimental group. You can also do so manually, by flipping a coin or rolling a dice to randomly assign participants to groups.

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Home » Blog » Comprehensive Guide to Research Methodology – Design | Methods | Best Practices

Comprehensive Guide to Research Methodology – Design | Methods | Best Practices

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Table of Contents

• Introduction
• Steps in Research Process
• Classification of Research Design

1. Introduction

This article describes the research process and different research designs in detail. Management and social science research, like other forms of scientific inquiry, require a structured sequence of highly interrelated steps (Zigmund et al., 2010). The research process involves a series of steps or actions essential for the smooth conduct of any research. The figure below illustrates the sequence of the research process. It is to be noted that these steps are not a road map to all kinds of research. Basically, it is applicable for deductive or functionalist research, and it can or needs to be revised to suit the requirements of a specific project. The research process doesn’t need to be followed successively; rather, the steps overlap frequently and are interrelated. The research process offers a comprehensive guideline that can be referred to for any management and social science research. It may happen that later stages can be accomplished before the earlier stages.

The steps involved in the research process are neither mutually exclusive nor separate and distinct. The selection of a research topic at the outset, defining the research problem and objectives, influences the selection of a sample and data collection. The sample selection may affect the design of questionnaire items. For example, suppose an organization wants to know the cause of attrition among lower-category employees with low educational qualifications. In that case, the wording for the questionnaire will be easier than for people in top management positions with professional educational qualifications. The steps may differ based on the objectives of the research. However, research based on deductive logic should follow the steps outlined below:

2. Steps in Research Process

• Problem Identification
• Literature Review
• Formulating Research Questions
• Research Design
• Data Collection
• Data Analysis
• Conclusions and Report Writing.

The quest for research must always be triggered by the longing to explore and gain more knowledge and understanding. The management dilemma encourages the need for a decision. The need may arise owing to the cause that the researchers want to discover or reestablish certain relationships. The orientation might be to solve immediate management issues, discover something new, or have purely academic intentions. For instance, in an organization, the manager may want to know the reason for high attrition and lack of job satisfaction, or a retail store may survey the post-purchase satisfaction among the customers.

2.1 Research Problem Identification

Defining the research problem is the first step in the research process. The researchers get the proper direction to conduct their research by first understanding the research problems. Hence, a well-defined research problem is crucial. When the problem is discovered, researchers and management can take further steps to define the problem clearly and precisely. A problem defined with accuracy and conscience helps the researchers utilize the available resources effectively. It is imperative for researchers to explore what exactly is the problem and what are the objectives of the research. The rule generally followed to define the research problem is that the definition should permit the researchers to acquire all details required to address the managerial issues and show guidelines for finding a solution. The researcher should be careful not to define the problem too broadly or narrowly. Examples of broad managerial problems are defining a strategy for enhancing organizational performance and a strategy to elevate the organization’s brand equity. An example of a narrow definition of a problem is how to match competitors’ recruitment strategies. To overcome the possibility of both errors while defining the research problem, the researchers must define the problem with broad, popular terms and devise its components. The broad general statement helps the researchers get a sound perspective on the research problem and avoid the error of defining the problem narrowly. On the other side, the specific component helps to identify the key aspects of the research problem, extend a transparent guideline to proceed further and avoid the error of defining the problem too broadly. In management and social science research, broad management problems need to be converted to information-oriented research problems that focus more on the cause than the symptoms. Some examples of managerial problems converted to research problems are presented in Table below. The conversion of management dilemma to managerial questions and further to research questions can be carried out through exploratory research. Such research incorporates an examination of past research studies, a review of extant literature and organizational records and interviewing experts (Cooper et al., 2016).

2.2 Literature Review

Exploring the existing literature is critical in the research process. Researchers must explore and investigate extant literature to observe whether other researchers have already addressed the identified research problem. A literature review is a systematic search of published work, including periodicals, books, journal papers (conceptual and empirical), and reports, representing theory and empirical work about the research problem and topic at hand. A survey of existing literature is customary in applied research and is an elementary requirement of a basic research report. The internet, electronic databases, websites, and e-library help the researcher to carry out literature surveys systematically and easily.

The literature review aims to study the existing state of knowledge in the domain of interest, to picture key authors, theories, methods, topics, and findings in that domain, and to explore the gaps in knowledge in that domain. A literature review conducted systematically reveals whether initial research questions have already gained substantial attention in the extant literature, whether more interesting newer research questions are available, whether past studies have consistent findings or contradictions exist, flaws in the body of research that the researchers can address, and whether the initial research questions need to be revised as per the findings of the literature review. Furthermore, the review can answer the proposed research questions and help identify theories used in previous studies to address similar research questions. For example, for an organization interested in determining the true cause of turnover, the researcher will study extensively the existing literature on attrition and its causes. By studying relevant journal articles, books, and book chapters, the researcher will discover the causes of attrition in general, find out the existing gaps, and suggest the management carry forward the research to find causes specific to the organization.

As deductive research primarily involves theory testing, the researchers must identify one or more theories that can illuminate the proposed research questions. Through an extensive literature review, researchers may uncover various concepts and constructs related to the phenomenon of interest. A theory will extend support to constructs/variables that are logically relevant to the chosen phenomenon. In the deductive approach, researchers use theory/theories as the logical basis for hypothesis testing. However, researchers must carefully select the theories appropriate for the identified problem to be studied. The hypotheses need to be logically formulated and connected to the research objectives.

2.3 Formulating Research Questions

After problem identification and clarification, with or without an exploratory research approach, the researchers should derive the research objectives. Cautious attention to problem definition helps the researchers devise proper research objectives. Research objectives are the goal to be achieved through research. The research objective drives the research process further. A well-devised research objective enhances the possibility of gathering, relevant information and avoiding unwanted information. The research objectives can be properly developed with the consensus of the researchers and management on the actual managerial and business problems. The researcher should ensure that the research objectives are clearly stated, appropriate, and will yield germane information. The research objective may involve exploring the likelihood of venturing into a new market or may necessitate examining the effect of a new organizational policy on employee performance. The nature and types of objectives lead to choosing an appropriate research design.

Research Objectives:  Research objectives represent the goal of the research the researchers want to accomplish.

2.3.1 Suitable Research Questions

Research questions are important to conduct effective research. Without a clear research question, the researcher may face the risk of unfocused research and will not be sure of what the research is about. Research questions are refined descriptions of the components of the research problem. These are questions related to behavior, events or phenomena of interest that the researchers search for answers in their research. Examples include what factors motivate the employees in an organization to apply the gained knowledge back to their jobs or what needs to be done to enhance the creativity of school-going students. Research questions can best state the objectives of the research. Each component of the research problem needs to be broken down into sub-parts or research questions. Research questions inquire about the information essential concerning the problem components. Properly answered research questions will lead to effective decision-making. While formulating research questions, researchers should be guided by the problem statement, theoretical background, and analytical framework.

Sources of Research Questions

• Extant Literature
• Personal experience
• Societal issues
• Managerial problems
• New theories
• Technological advancement
• Empirical cases
• Contradictory finding

2.3.1.1 Significance of Research Questions

Research questions are critical because they guide scientific and systematic literature search, the decision about appropriate research design, the decision about data collection and target audience, data analysis, selection of right tools and techniques and overall to move in the right direction.

The researcher can utilize different sources for formulating research questions, such as extant literature, personal experience, societal issues, managerial problems, new theories, technological advancement, and contradictory findings. The research question must portray certain attributes. Research questions in quantitative research are more specific compared to qualitative research. Sometimes, some qualitative research follows an open approach without any research questions. The main steps involved in formulating research questions are illustrated in Figure below.

Criteria of Effective Research Questions

• Rateability
• Systematic and logical
• Significant
• Fascinating
• Logical association among variables

The sequence in selecting research questions suggests that the researchers are engrossed in a process of progressive focusing down when developing the research questions. It helps them to slide down from the general research area to research questions. While formulating the research questions, the researchers should understand that ending a research question with a question mark is essential. Without a question mark, a statement cannot be considered as a research question. It is quite possible that the researchers may not get answers to all research questions. The research questions need to be related to each other.

2.4 Planning the Research Design

After formulating research problems and literature surveys, the next stage in the research process is to develop the research design. Research design is the blueprint of research activities to answer research questions. It is a master plan that includes research methods and procedures for gathering and analyzing the relevant information with minimum cost, time, and effort. A research design extends a plan for carrying out the research. The researchers need to decide the source to collect information, the techniques of research design (survey or experiment), sampling techniques, and the cost and schedule of the research. The success of these objectives depends on the purpose of the research. Usually, research purposes are segregated into four types: exploration, description, diagnosis, and experimentation.

There are varied designs, such as experimental or non-experimental hypotheses testing (details of different research designs are outlined in section 2.3 in this chapter). There are four primary research methods for descriptive and causal research: survey, experiments, secondary data, and observations. The selection of an appropriate research method relies on the research objectives, available data sources, the cost and effort of collecting data, and the importance of managerial decisions. If the research objective is exploration, a flexible research design can extend better opportunities to investigate different aspects of the research problem. On the other hand, if the intention is simply to describe any situation or phenomena of interest to examine the relationship between two or more variables, the appropriate design should prioritize minimizing bias and maximizing reliability in data collection and analysis. For example, suppose a researcher wants to conduct exploratory research to know the different types of arthritis common in India. In that case, it may require a flexible design relying on secondary data from hospital records or discussions with doctors or other experts to reach conclusions. However, to invent COVID-vaccination and medicine for the COVID-19 virus, the researchers conducted varied experiments to reach a conclusion.

2.4.1 Hypotheses Development

Exploratory research helps the researchers define the research questions, key variables, and theoretical underpinnings and formulate hypotheses if required in the research. The hypotheses must be logically derived based on the research questions and linked to research objectives. A hypothesis is a tentative proposition regarding a research phenomenon. It may be a tentative statement that indicates an association between two or more variables, guided by any supportive theory, theoretical framework, or analytical model. It is a viable answer to the research questions framed by the researchers. Hypotheses are statements of relationships or propositions that are declarative and can be tested with empirical data. Some examples are:

H 1 : Training influences organizational performance.

H 2 : Training enhances employee performance.

For two more research questions i.e., “to what extent does brand love determine purchase intention?” and “does age and family background moderate the relationship?”, the hypotheses are:

H 1 : Brand love is related to purchase intention.

H 2 : Age and Family status moderate the association between brand love and purchase intention. Figure below provides a pictorial representation of the hypotheses drawn.

However, it is not always feasible for researchers to formulate hypotheses in all situations. Sometimes, researchers may lack all relevant information, and theoretical support may not be available to formulate the hypotheses.

2.5 Sampling Design

This stage of the research process involves an investigation of the population under study. A complete investigation of the population under study is known as a census inquiry. Usually, in census investigation, all units or items of the population are studied with high accuracy and reliability. However, it is usually not practicable and feasible for the researchers to study the entire population. Researchers usually prefer to investigate small, representative subgroups from the population known as sample. The procedure to select the sub-groups/samples is called sampling design. Sampling entails the process of drawing conclusions based on a subgroup of the population. Hence, the sample is a subset of the population. The first question that needs to be addressed in sampling is “who is to be included in the sample?” and this requires the identification of the target population under study. It is difficult for the researcher to define the population and sampling unit. For example, if a researcher wants to investigate the financial savings and vehicle loan association survey. In that case, individuals with existing accounts will be taken, and this sample unit represents the existing customers and not the potential customers. Hence, it is critical in sampling design to determine the specific target population.

Secondly, the issue that concerns the researchers in sampling design is selecting an appropriate sample size, and the third concern is selecting the sampling units. Researchers need to address these concerns to justify the research. Samples can be selected either using probability sampling techniques or non-probability sampling techniques. There are four types of probability sampling such as simple random, systematic, stratified, and cluster sampling. Non-probability sampling includes convenience, judgmental, quota, and snowball sampling. Depending on the objective, researchers should select the appropriate sampling techniques for their study.

2.6 Fieldwork and Gathering Data

After the formalization of the sampling plan, the fieldwork and data-gathering stage begins. The researcher gathers data after finalizing what to research, among whom, and which method to use. Data gathering involves the process of information collection. Different data collection instruments are available for researchers to collect information or data. Broadly, there are two ways to collect data, such as primary and secondary data collection methods. Primary data include data collected firsthand and are original. Varied methods are available for primary data collection, such as structured and unstructured interviews, focused group discussion, observation, and survey using a structured questionnaire. The data can be collected offline or online. Secondary data included information collected from published or unpublished sources that were already available. Some secondary data collection sources are articles, magazines, company records, expert opinion survey data, feedback of customers, government data, and past research on the subject. For example, to conduct a survey of job satisfaction in an organization, the researcher may circulate a printed questionnaire offline or mail the questionnaire to the selected respondents following an appropriate sampling technique.

Another example could be a study that investigates the purchase preference for luxury cars, and the base model demands primary and empirical information. However, another study that intended to describe the financial investment behavior of existing customers will use secondary data. At this stage, the researchers need to ensure the reliability and validity of the data obtained for the study.

2.7 Data Processing and Analysis

After data gathering, the data needs to be converted or properly coded to answer the research question under study. The information gathered in the data collection phase should be mined from the primary raw data. Data processing starts with data editing, coding, and tabulation. First, it is vital for the researchers to check the data collection forms for missing data, clarity, and consistency in categorization. The editing process involves problems associated with data, such as respondents’ response errors. Editing improves the quality of the data and makes the data usable for tabulation, analysis, and interpretation. Tabulation is a technical process in which classified data are presented in tables. Researchers use computers to feed data to a computer spreadsheet for data analysis. The preparation of a spreadsheet also requires lots of expertise and experience.

After coding the data, the next step is to analyze the data. Data analysis is the utilization of reasoning to make sense of data gathered. Ample statistical techniques are available for the researchers to analyze the data. Based on the research questions, objectives, study types, sampling framework used, data types, and degree of accuracy involved in the research, one can choose from parametric or non-parametric techniques for data analysis. Researchers may adopt univariate, bi-variate or multi-variate methods for data analysis. The analysis may include simple frequency analysis, multiple regression, or structural equation modeling. Different techniques are available for qualitative data, presented in Part 3 of this book.

2.8 Drawing Conclusion and Preparing a Report

After data analysis, the final stage in the research process is the interpretation of the results. The researcher requires analytical skills to interpret the statistical results, link the output with the research objectives, and state the implications of the result.

Research Design:  Research design is the blueprint/systematic steps to carry out research smoothly

Finally, researchers must communicate the result in the form of a report. The preparation of the final report needs to be done with the utmost care. The final report should include the identified research questions, research approach, data collection method, data analysis techniques, study findings, and implications for theory and practice. The structure of the report will be discussed in the last section of this book. The report should be prepared comprehensively to be usable by management or organizations for decision-making.

3. Classification of Research Design

This section highlights the classification of research design. As mentioned in the previous section, research design is the framework for carrying out management and other research. After the identification of a problem, the researchers formulate the research design. A good research design ensures the effectiveness of the research work. The choice of selecting an appropriate design relies on the research objectives. The broad categorization of research design with sub-categorization is detailed in various sub-sections.

3.1 Exploratory Research Design

Methods to Conduct Exploratory Research

• Literature survey
• Secondary sources of data
• Experience survey
• Focused group discussions
• Observations
• Structured and unstructured interviews
• Pilot surveys
• Case Studies

Exploratory research design is the simplest form of research design. The researchers explore the true nature of the problem. When researchers aim to study a new area or examine a new interest, exploratory design is a good option. This research design is flexible and versatile in approach. The information required by the researchers is defined loosely and unstructured. Researchers carrying out qualitative research usually adopt exploratory research design. Exploratory research design serves three purposes (a) it helps the researchers to address their inquisitiveness and quest for better understanding (b) to assess the practicality of carrying out border research (c) and devise methods for further studies.

Methods to Conduct Descriptive Research

• Self-administered survey
• Phone survey
• Mail survey/online survey
• Observation
• Personal interview
• Telephone interview

Exploratory research design has paramount significance in management and social science research. They are crucial for researchers who want to study something new. To cite an example, during the COVID-19 pandemic, physical health, mental health, and safety of school and college-going children were a concern for most people. The online education system was the new normal at that time. Research studying the impact of digitalization, long time spent in online studies on students’ health and mental well-being during the COVID-19 pandemic, is of an exploratory kind. One of the disadvantages of exploratory research design is that researchers rarely get specific answers to the research questions.

3.2 Descriptive Research Design

The prime objective of descriptive research design is to describe certain situations or events. This type of design provides an extensive explanation of the research phenomena under study. In descriptive research, the researchers possess prior knowledge about the problem situations. The information is defined with clarity. This kind of research is preplanned and more structured than exploratory research. Researchers must formulate research questions properly and have clarity regarding the types of data needed and the procedure to be followed to achieve the research objectives. Researchers have the luxury of covering a large representative sample. Researchers must answer five Ws and one H – what, who, when, where, why, and how of research issues. What kind of information is required for the research, who are the target respondents, when the information will be collected, where to interact with the respondents, why information is collected from the respondents and how to collect data from the respondents. Descriptive research studies can be cross-sectional or longitudinal. The major objectives for the following descriptive research are given below.

• To explain the characteristics of certain groups such as the Indian population, employees, students, marketing personnel, organizations, sales persons. For example, a university to design a customized online higher studies course for working professionals needs a holistic profile of the interested population.
• To evaluate the portion of individuals in a specific population portraying a typical behavior. For instance, when a researcher is inclined to know the percentage of employees not interested in an online platform introduced for them in their organization.
• To predict for future. For instance, to know the future of physical retail stores due to the widespread expansion of online stores.
• To examine the extent to which management research variables relate to each other. For example, to what extent does work-life balance, salary, and conducive work environment enhance employee job satisfaction?

3.3 Causal Research Design

Usually, causal research design is adopted by researchers to explain causal relationships among phenomena under study. Causal research examines cause-and-effect relationships among variables. Causal research has certain criteria, as already discussed in Chapter 1. Causal research follows a planned and structured design like descriptive research. Though the magnitude of the relationship among variables is examined in descriptive research, the causal association cannot be explained through such research. Experimentation is one of the methods for carrying out causal research.

In causal research, the researchers usually examine the impact of one variable on another. The researchers try to explore the cause-and-effect relationship (nomothetic explanation). How can the researcher know whether cause and effect are associated? There are three criteria for a nomothetic causal relationship when (1) two or more variables are correlated, (2) the cause precedes the effect and (3) the absence of a plausible alternative explanation for the effect other than the proposed cause (Babbie, 2020). First, without establishing a correlation among two or more variables, causation cannot exist. Second, the cause should happen before the effect in time. For instance, it is more sensible to say that children’s religious affiliation is caused by their parents than to reflect that parents’ religious affiliation is due to children; even in some cases, it is plausible that children may convert to other religions later with their parent’s permission. The third significant condition for a causal relationship is that the effect cannot be attributed to any external third variable for establishing causation.

To cite one classic example, there is a causal association between sales of ice cream and death owing to drowning. Intake of more ice creams in summer does lead to a higher death rate due to drowning. The third intervening variable that causes higher death is season or temperature. In summer, higher deaths occur due to swimming and not because of taking ice-creams. The intervening variable season or temperature causes a higher death rate.

To establish a reliable causal relationship among two or more variables, other influencing variables must be controlled to neutralize their impact on the studied variables. For example, to study the effect of factors influencing training transfer in soft skill training, the other intervening variables such as age, gender, and educational qualification need to be controlled. This kind of research sometimes demands experimentation to establish causality. In most cases, causal research is quantitative and needs statistical hypothesis testing.

3.4 Experimental Research Design

Experimental research aims to examine the cause-effect relationship in a controlled setting by isolating the cause from the effect in time. The three criteria suggested by John Stuart Mill mirror in experimental research. In experimental research, the cause is administered to one group of subjects, known as the treatment group and not to the control group, and the researchers observe the difference in mean effect among the subjects of both groups. Whether variation in the cause is connected to variation in effect is observed. To be more specific, the researcher manipulates the independent variable and examines the change in the dependent variable, keeping other variables constant. Researchers used varied methods during the experiments to reduce the plausible effect of other explanations for the effect, along with ancillary methods to investigate the plausibility of those that cannot be ruled out. It is vital in experimental studies to control the extraneous and confounding variables while carrying out the experiments. Ignorance of such variables may lead to spurious relationships among studied variables. However, bringing many of the variables under experimental control is impossible. For example, personal characteristics of the subject like age, sex, intelligence, beliefs and persona. In such cases, the researchers must observe natural variations in the variables of concern. Then, statistical procedures are used to rule out the plausible impact of uncontrolled factors.

Experimental Research Design:  An experiment is a method of collecting evidence to indicate the effect of one variable on another.

Experimental research design can be conducted in a laboratory setting (laboratory experiment) or in a field setting (field experiments) where the phenomena of research interest happen. As an example, one of the most talked about and controversial experiments conducted on understanding human behavior has been the Stanford Prison Experiments, which took place at Stanford University in 1971. The experiments were funded by the US Office of Naval Research, and the principal investigator for the same was Prof Phillip Zimbardo. The major purpose of these experiments was to understand how norms develop and social expectations about roles shape group behavior. Experimental studies are segregated into four categories such as pre-experimental, true-experimental, quasi-experimental and statistical design.

3.4.1 Correlation, Causation and Cofounds

Correlation cannot be treated as causation, and correlation does not always prove causation. In correlation, it is unclear which variable comes first or whether any alternative explanation exists for the assumed effect. Two variables may be correlated due to chance. Correlation is symmetric, while causation is asymmetric. Two variables may be co-related, but their relationship may be affected by a third variable called cofounds. For example, let’s say that high salary and high educational qualifications are correlated. It is difficult to say with confirmation which comes first. Whether a high educational qualification leads to a high salary, or a high salary leads to a high educational qualification. Both possibilities can hold true and necessitate further investigation. Until researchers conclude through their investigation, a mere correlation among these two variables will not give a clear picture of their causal relationship. There is also the possibility of an alternative explanation for the relationship between high salary and high educational qualifications. The link may be due to a third variable called intellect, which results in high salary and high educational qualifications.

In management research, social science, and natural science, three significant pairs of components are required for experimentation: Experimental and control group, independent and dependent variable, and pre-test and post-test.

3.4.1.1 Experimental and Control Group

The group in which an experimental treatment is administered is known as the experimental or treatment group. In contrast, the group in which no experiment is administered is known as the control group. Using control groups enables the researchers to assess the experiment’s effects. For example, suppose a researcher wants to study the impact of rewards on employee productivity in an organization. In that case, the researcher can experiment with two groups of employees. One group will be given external rewards, known as the experimental group, and the other group (control group) will provide no external rewards. Then, the researcher can investigate the causal association between rewards on employees’ productivity through this experiment. The use of a control group is quite common in medical science research. In social science and management research, the use of control groups and experimental studies became popular with several experiments conducted in the late 1920s and early 1930s by F. J. Roethlisberger and W. J. Dickson (1939) to discover the changes required in working conditions to enhance employee satisfaction and productivity. Their series of experiments resulted in the Hawthorne effect.

3.4.1.2 Independent and Dependent Variables

In experimental research, the researchers study the impact of an independent variable on the dependent variable. Usually, experimental stimuli, whether present or absent, are considered independent variables. Independent variables are manipulated in the study, and their effects are assessed and compared. The researchers compare outcomes when the stimulus is present and not present. Hence, the independent variable is the cause, and the dependent variable is the presumed effect. It is to be noted that the independent variable in one study may serve as a dependent variable in another study. For example, an experiment intends to explore the causality between high salary and job satisfaction, job satisfaction is the dependent variable. However, in another experiment designed to explore the causality between job satisfaction and employee productivity, job satisfaction is the independent variable.

3.4.1.3 Pre- and Post-test

In an experiment, the experimenters measure the variable before conducting the experiment on the group known as the pre-test and measure the variable after conducting the experiments is called as post-test. Hence, subjects are exposed to a stimulus called a dependent variable (pre-testing), then exposed to a stimulus, i.e., independent variable, and again assessed with a dependent variable (post-testing). Any discrepancies between the two measurements of dependent variables are ascribed to the independent variable.

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The effect of augmented reality on learning meiosis via guided inquiry and pecha kucha: a quasi-experimental design.

1. Introduction

1.1. inquiry-based learning and guided inquiry, 1.2. pecha kucha, 1.3. ar and ar application, 2. materials and methods, 2.1. experiment plan, 2.2. ar app división meiótica 3d, 2.3. knowledge assessment tests, 2.4. statistical analyses, 3.1. students learning performance on post-test (q1), 3.2. students learning performance on follow-up test (q2), 3.3. students learning performance when using ar with guided inquiry and pecha kucha (q3), 3.4. students learning performance when using only guided inquiry and pecha kucha (q4), 4. discussion, 5. conclusions, author contributions, institutional review board statement, informed consent statement, data availability statement, conflicts of interest.

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Faria, A.; Lobato Miranda, G. The Effect of Augmented Reality on Learning Meiosis via Guided Inquiry and Pecha Kucha: A Quasi-Experimental Design. Information 2024 , 15 , 566. https://doi.org/10.3390/info15090566

Faria A, Lobato Miranda G. The Effect of Augmented Reality on Learning Meiosis via Guided Inquiry and Pecha Kucha: A Quasi-Experimental Design. Information . 2024; 15(9):566. https://doi.org/10.3390/info15090566

Faria, António, and Guilhermina Lobato Miranda. 2024. "The Effect of Augmented Reality on Learning Meiosis via Guided Inquiry and Pecha Kucha: A Quasi-Experimental Design" Information 15, no. 9: 566. https://doi.org/10.3390/info15090566

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