Which statement best characterizes the design techniques to avoid bias in clinical trials?

• A. The most important design techniques for avoiding bias are blinding and randomization.
• B. Blinding is optional in most studies.
• C. Randomization is less important than sample size.
• D. Only blinding matters; randomization is unnecessary.

Answer: (C)

Bias in clinical trials is best controlled by using randomization and blinding. Randomization prevents selection bias and balances known and unknown prognostic factors across groups, so comparisons are fair and not driven by who was chosen for each group. Blinding reduces performance and detection bias by keeping participants, clinicians, and outcome assessors unaware of the assigned treatment, so care, behavior, and assessments aren’t influenced by expectations. The sample size affects power and precision, not the fundamental bias introduced by design, so a larger study can still be biased if randomization and blinding are flawed. Therefore, the design techniques that most effectively avoid bias are randomization and blinding, rather than focusing on sample size alone or deeming either technique optional.