The control group is composed of participants who do not receive the experimental treatment. When conducting an experiment, these people are randomly selected to be in this group. They also closely resemble the participants who are in the experimental group, or the individuals who receive the treatment.
While they do not receive the treatment, they do play a vital role in the research process. Experimenters compare the experimental group to the control group to determine if the treatment had an effect. By serving as a comparison group, researchers are able to isolate the independent variable and look at the impact it had.
- "To assess the impact of the independent variable, we must have at least two different treatment conditions so that we can compare the effect of different values of the independent variable. At times, one condition is an experimental condition and the other is a control condition... The control condition is used to determine the value of the dependent variable without and experimental manipulation of the independent variable. The subjects in a control condition are called a control group. In the control condition, we carry out exactly the same procedures that are followed in the experimental condition, except for the experimental manipulation."
(Myers & Hansen, 2012)
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Myers, A. & Hansen, C. (2012) Experimental psychology. Belmont, CA: Cengage Learning