What should the protocol specify to minimize bias?

• A. Randomization is the only method needed to minimize bias.
• B. Blinding is unimportant if outcomes are objective.
• C. Compliance monitoring alone ensures unbiased results.
• D. Protocol should specify methods of allocation to treatment groups and blinding.

Answer: (D)

Minimizing bias in a trial comes from controlling two key areas: how participants are assigned to treatment groups and who remains unaware of those assignments during the study. A protocol should explicitly lay out the methods of allocation to treatment groups (including how randomization will occur and how allocation will be concealed) and how blinding will be implemented (who will be blinded, to what, and under what circumstances unblinding is allowed). Randomization reduces selection bias by preventing predictable assignment, while allocation concealment stops investigators from influencing group assignment. Blinding reduces biases in treatment administration, participant behavior, and outcome assessment, which helps ensure that differences observed are due to the interventions rather than expectations or measurement imprecision. Even when outcomes are objective, blinding remains important to prevent bias in data collection and interpretation. In contrast, relying on compliance monitoring alone or assuming randomization suffices without a clear blinding plan leaves room for bias to creep in.