In a randomized clinical trial, what is the major purpose of random assignment?

In a randomized clinical trial, what is the major purpose of random assignment?

• A. Represent the general population
• B. Reduce selection bias in allocation of treatment
• C. Facilitate double blinding (masking)
• D. Ensure comparable baseline characteristics

Answer: (B)

Random assignment provides each participant with an equal chance of receiving any treatment, which stops investigators or participants from steering the allocation based on prognosis or preferences. This prevents selection bias and helps balance both known and unknown prognostic factors across groups, so differences in outcomes are more likely due to the treatment itself. While randomization often leads to similar baseline characteristics and can support blinding when allocation is concealed, its central function is preventing biased allocation. Representing the general population is about how participants are sampled, not how they’re allocated, and blinding is a separate design feature that may be facilitated by concealment and placebo controls rather than by randomization alone.

Random assignment provides each participant with an equal chance of receiving any treatment, which stops investigators or participants from steering the allocation based on prognosis or preferences. This prevents selection bias and helps balance both known and unknown prognostic factors across groups, so differences in outcomes are more likely due to the treatment itself. While randomization often leads to similar baseline characteristics and can support blinding when allocation is concealed, its central function is preventing biased allocation. Representing the general population is about how participants are sampled, not how they’re allocated, and blinding is a separate design feature that may be facilitated by concealment and placebo controls rather than by randomization alone.