What Is a Control Group?

Table of ContentsView AllTable of ContentsControl Group vs. Experimental GroupImportanceTypes of Control GroupsExamplesUses

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Table of Contents

Control Group vs. Experimental Group

Importance

Types of Control Groups

Examples

Uses

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In simple terms, the control group comprises participants who do not receive the experimental treatment. When conducting an experiment, these people are randomly assigned to this group. They also closely resemble the participants who are in the experimental group or the individuals who receive the treatment.

Experimenters utilize variables to make comparisons between an experimental group and a control group. Avariableis something that researchers can manipulate, measure, and control in an experiment. The independent variable is the aspect of the experiment that the researchers manipulate (or the treatment). The dependent variable is what the researchers measure to see if the independent variable had an effect.

While they do not receive the treatment, the control group does play a vital role in the research process. Experimenters compare theexperimental groupto the control group to determine if the treatment had an effect.

By serving as a comparison group, researchers can isolate theindependent variableand look at the impact it had.

The simplest way to determine the difference between a control group and an experimental group is to determine which group receives the treatment and which does not. To ensure that the results can then be compared accurately, the two groups should be otherwise identical.

Control GroupNot exposed to the treatment (the independent variable)Used to provide a baseline to compare results againstMay receive a placebo treatmentExperimental GroupExposed to the treatmentUsed to measure the effects of the independent variableIdentical to the control group aside from their exposure to the treatment

Control GroupNot exposed to the treatment (the independent variable)Used to provide a baseline to compare results againstMay receive a placebo treatment

Not exposed to the treatment (the independent variable)

Used to provide a baseline to compare results against

May receive a placebo treatment

Experimental GroupExposed to the treatmentUsed to measure the effects of the independent variableIdentical to the control group aside from their exposure to the treatment

Exposed to the treatment

Used to measure the effects of the independent variable

Identical to the control group aside from their exposure to the treatment

Why a Control Group Is Important

While the control group does not receive treatment, it does play a critical role in the experimental process. This group serves as a benchmark, allowing researchers to compare the experimental group to the control group to see what sort of impact changes to the independent variable produced.

Because participants have beenrandomly assignedto either the control group or the experimental group, it can be assumed that the groups are comparable.

Any differences between the two groups are, therefore, the result of the manipulations of the independent variable. The experimenters carry out the exact same procedures with both groups with the exception of the manipulation of the independent variable in the experimental group.

There are a number of different types of control groups that might be utilized in psychology research. Some of these include:

Examples of Control Groups

Control groups can be used in a variety of situations. For example, imagine a study in which researchers example how distractions during an exam influence test results. The control group would take an exam in a setting with no distractions, while the experimental groups would be exposed to different distractions. The results of the exam would then be compared to see the effects that distractions had on test scores.

Experiments that look at the effects of medications on certain conditions are also examples of how a control group can be used in research. For example, researchers looking at the effectiveness of a new antidepressant might use a control group that receives a placebo and an experimental group that receives the new medication. At the end of the study, researchers would compare measures of depression for both groups to determine what impact the new medication had.

After the experiment is complete, researchers can then look at the test results and start making comparisons between the control group and the experimental group.

Waitlist Control Groups in Psychology Experiments

Uses for Control Groups

Researchers utilize control groups to conduct research in a range of different fields. Some common uses include:

4 SourcesVerywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Malay S, Chung KC.The choice of controls for providing validity and evidence in clinical research.Plast Reconstr Surg.2012 Oct;130(4):959-965. doi:10.1097/PRS.0b013e318262f4c8National Cancer Institute.Control group.Pithon MM.Importance of the control group in scientific research.Dental Press J Orthod.2013;18(6):13-14. doi:10.1590/s2176-94512013000600003Karlsson P, Bergmark A.Compared with what? An analysis of control-group types in Cochrane and Campbell reviews of psychosocial treatment efficacy with substance use disorders.Addiction. 2015;110(3):420-8. doi:10.1111/add.12799Additional ReadingMyers A, Hansen C.Experimental Psychology. Belmont, CA: Cengage Learning; 2012.

4 Sources

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Malay S, Chung KC.The choice of controls for providing validity and evidence in clinical research.Plast Reconstr Surg.2012 Oct;130(4):959-965. doi:10.1097/PRS.0b013e318262f4c8National Cancer Institute.Control group.Pithon MM.Importance of the control group in scientific research.Dental Press J Orthod.2013;18(6):13-14. doi:10.1590/s2176-94512013000600003Karlsson P, Bergmark A.Compared with what? An analysis of control-group types in Cochrane and Campbell reviews of psychosocial treatment efficacy with substance use disorders.Addiction. 2015;110(3):420-8. doi:10.1111/add.12799Additional ReadingMyers A, Hansen C.Experimental Psychology. Belmont, CA: Cengage Learning; 2012.

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Malay S, Chung KC.The choice of controls for providing validity and evidence in clinical research.Plast Reconstr Surg.2012 Oct;130(4):959-965. doi:10.1097/PRS.0b013e318262f4c8National Cancer Institute.Control group.Pithon MM.Importance of the control group in scientific research.Dental Press J Orthod.2013;18(6):13-14. doi:10.1590/s2176-94512013000600003Karlsson P, Bergmark A.Compared with what? An analysis of control-group types in Cochrane and Campbell reviews of psychosocial treatment efficacy with substance use disorders.Addiction. 2015;110(3):420-8. doi:10.1111/add.12799

Malay S, Chung KC.The choice of controls for providing validity and evidence in clinical research.Plast Reconstr Surg.2012 Oct;130(4):959-965. doi:10.1097/PRS.0b013e318262f4c8

National Cancer Institute.Control group.

Pithon MM.Importance of the control group in scientific research.Dental Press J Orthod.2013;18(6):13-14. doi:10.1590/s2176-94512013000600003

Karlsson P, Bergmark A.Compared with what? An analysis of control-group types in Cochrane and Campbell reviews of psychosocial treatment efficacy with substance use disorders.Addiction. 2015;110(3):420-8. doi:10.1111/add.12799

Myers A, Hansen C.Experimental Psychology. Belmont, CA: Cengage Learning; 2012.

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