A randomised controlled trial (RCT) is a study in which a group of similar participants are randomly assigned to 2 (or more) groups to test a treatment, drug or other intervention.
Participants in one group (the intervention or experimental group) receive the intervention being tested while participants in the other group (the comparison or control group) receive no treatment, a placebo or an alternative treatment. Participants in both groups are followed for pre-determined lengths of time to measure the effect of the intervention: statistical methods are used to measure any differences in response between the groups
Cluster randomised trial Quasi-randomisation Random allocation Randomisation