control group

A group of persons that serves as the basis of comparison for assessing the effects of the intervention applied to the subjects in the treatment group.

Note: Depending on the circumstances of the trial, a control group may receive no treatment, the usual or standard treatment, or a placebo. To make the comparison valid, the composition of the control group must resemble that of the treatment group as closely as possible.

(Related concepts: randomization, concurrent control, historical control)