In an experiment that focuses on the effects of a single condition or variable, the control group is exposed to all the conditions or variables except the one being studied.
Scientists often study how a particular condition or factor influences an outcome. In an experiment in which there are two groups of subjects, the group that is exposed to the condition or factor is called the experimental group. The other group, the control group, is not exposed to that factor, and thus provides a basis for comparison. For example, in a study of the influence of loud music on the test performances of children, the control group would be the group of children not exposed to loud music during their test. Their test scores would be compared with the experimental group, the group of children who were exposed to loud music during the test. In this type of experiment design, subjects would be randomly assigned to each group to ensure a reliable comparison.
See also Assessment, psychological ; Research methodology ; Validity .
Evans, Annabel, and Bryan J. Rooney. Methods in Psychological Research. Thousand Oaks, CA: SAGE, 2011.
Richard, David C. S., and Steven Ken Huprich. Clinical Psychology: Assessment, Treatment, and Research. Amsterdam: Elsevier/AP, 2009.