Control group — a group of participants in a study not receiving a particular intervention, used as a comparator to evaluate the effects of the intervention.

Random assignment — making a comparison group as similar as possible to the intervention group, to rule out external influences; randomly allocating individuals to either the intervention group or the control group.

Controls in a randomised control trial (RCT) are people in a comparison group. They receive the usual treatment (or a placebo) while the experimental group receive the treatment being tested. (CASP)