Randomized controlled trial
Also: RCT
In plain language
A study that randomly assigns people to a treatment or a comparison group, making it one of the most reliable ways to test whether a treatment works.
Technical definition
An experimental study design in which participants are randomly allocated to intervention or control groups, minimizing selection bias and confounding to support causal inference about an intervention's effect.
Randomization balances known and unknown differences between groups, which is why RCTs — especially when blinded and placebo-controlled — sit near the top of the evidence hierarchy for establishing cause and effect.