Randomized controlled trial

A randomized controlled trial (or randomized control trial;[2] RCT) is a form of scientific experiment used to control factors not under direct experimental control. Examples of RCTs are clinical trials that compare the effects of drugs, surgical techniques, medical devices, diagnostic procedures or other medical treatments.

Flowchart of four phases (enrollment, allocation, intervention, follow-up, and data analysis) of a parallel randomized trial of two groups (in a controlled trial, one of the interventions serves as the control), modified from the CONSORT (Consolidated Standards of Reporting Trials) 2010 Statement[1]

Participants who enroll in RCTs differ from one another in known and unknown ways that can influence study outcomes, and yet cannot be directly controlled. By randomly allocating participants among compared treatments, an RCT enables statistical control over these influences. Provided it is designed well, conducted properly, and enrolls enough participants, an RCT may achieve sufficient control over these confounding factors to deliver a useful comparison of the treatments studied.