Which statement best describes the purpose of randomization in clinical trials?

• A. To ensure equal numbers in each arm
• B. To maximize data collection speed
• C. To minimize selection bias and confounding
• D. To guarantee a favorable outcome

Answer: (C)

Randomization aims to prevent systematic differences between groups by evenly distributing both known and unknown factors that could influence the outcome. By assigning participants to intervention or control by chance, it guards against selection bias—decisions about who gets which treatment can’t be manipulated by researchers or participants—and against confounding factors that could distort comparisons. With prognostic factors balanced on average, observed differences in outcomes are more likely to reflect the effect of the intervention itself. This also supports the validity of the statistical analyses that assume comparable groups. Remember, randomization does not guarantee equal numbers in each arm, nor does it guarantee a favorable result; it just creates a fair comparison so the treatment effect can be estimated without bias. Allocation concealment helps maintain this integrity by preventing foreknowledge of assignments.