What is a defining feature of a randomized controlled trial (RCT)?

What is a defining feature of a randomized controlled trial (RCT)?

• A. Non-random assignment
• B. Random allocation to groups
• C. Not necessarily controlled
• D. Retrospective

Answer: (B)

Random allocation to groups ensures comparability at the start of the trial, balancing known and unknown factors so differences in outcomes can be attributed to the intervention rather than preexisting differences. This randomization is what defines a randomized controlled trial. Non-random assignment can introduce bias by creating groups that differ systematically; a study that isn’t controlled or is retrospective doesn’t provide the same level of evidence because it can’t guarantee the same baseline comparability. In practice, RCTs are prospective and include a control group, often with blinding, to further minimize bias.

Random allocation to groups ensures comparability at the start of the trial, balancing known and unknown factors so differences in outcomes can be attributed to the intervention rather than preexisting differences. This randomization is what defines a randomized controlled trial. Non-random assignment can introduce bias by creating groups that differ systematically; a study that isn’t controlled or is retrospective doesn’t provide the same level of evidence because it can’t guarantee the same baseline comparability. In practice, RCTs are prospective and include a control group, often with blinding, to further minimize bias.