Randomized controlled trial

A study that randomly assigns participants to an intervention or control group and compares their outcomes to estimate the intervention’s effects.

Randomization: A procedure that assigns units to groups by chance rather than by choice or a predictable rule. Chance assignment helps balance known and unknown participant differences between trial groups.
Treatment effect: The difference in outcomes attributable to an intervention under a specified causal model. A trial aims to estimate this difference by comparing assigned groups.
Clinical trial: A prospective study that evaluates health-related interventions in human participants. Randomized controlled trials are a major design used within clinical research.
Observational study: A study that measures exposures and outcomes without assigning participants to interventions. It can answer related questions when researchers do not randomize treatment.
Control group: A study group that provides a comparison for assessing outcomes in an intervention group. Its outcomes help estimate what might have happened without the intervention.
Estimand: A precise definition of the treatment effect a study intends to estimate. It clarifies which participants, outcomes, and treatment circumstances the trial addresses.
Pragmatic clinical trial: A clinical trial designed to estimate an intervention’s effects under routine healthcare conditions. It tests whether an intervention works in ordinary practice, not only controlled settings.
Quasi-experiment: A study that estimates intervention effects using an assignment process without full randomization. It seeks causal evidence when random assignment is infeasible or unavailable.
Placebo: An inactive treatment designed to resemble an active treatment in a study. A placebo can help separate an intervention’s specific effects from expectations and treatment rituals.
Sampling error: The difference between a statistic from a sample and the corresponding population quantity due to chance. Trial estimates vary because each enrolled sample is only one possible sample.

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