Randomized controlled trial

In a randomized controlled trial (RCT), participants are randomly assigned to receive either an intervention or control treatment (often usual care services). This allows the effect of the intervention to be studied in groups of people who are: (1) the same at the outset and (2) treated the same way, except for the intervention(s) being studied. Any differences seen in the groups at the end can be attributed to the difference in treatment alone, and not to bias or chance.