Randomized Controlled Trial
A study where participants are randomly assigned to receive a treatment or not, allowing researchers to measure its true causal effect by comparing the two groups.
A research study in which participants are randomly assigned to either receive an intervention (treatment group) or a control condition (no treatment or standard care). By using random assignment, researchers can isolate the causal effect of the intervention, since the groups are statistically equivalent at the start. This design is considered the gold standard for testing whether a treatment actually works.
What this means in real life
A school randomly assigns half its students to a new tutoring program and keeps the other half learning normally, then compares test scores between groups. Because students were randomly assigned, any score difference can be attributed to the tutoring, not to which students were already stronger.
What it isn’t
It is not simply any study that measures an outcome before and after. A study where people self-select into a program (e.g., motivated volunteers) and are compared to non-participants is observational, not a true experiment, because the groups differ in ways beyond the treatment.
Commonly misused online
People often call any medical study a 'randomized controlled trial' even when participants chose their own treatment or were assigned based on availability rather than random chance. True randomization requires a neutral process like coin flips or computer assignment.
Based on 1 reference source, including government sources. Last verified July 16, 2026.