Which type of study design is considered the best method to minimize bias in clinical research?

Correct answer: D. Randomized controlled trial

• A. Case-control studies are retrospective and observational, so they are highly prone to recall and selection bias.
• B. Cohort studies are stronger than case-control but remain observational; confounding and loss to follow-up still introduce bias.
• C. Cross-sectional studies capture a single point in time and cannot establish temporality, so causation and bias control are weak.
• D. Correct. Randomization distributes known and unknown confounders evenly between groups, and blinding/controls minimize bias — the RCT sits at the top of the evidence hierarchy for therapy questions.