Which study design best eliminates BIAS?

Correct answer: D. Randomization (randomized controlled trial)

• A. Cohort studies can minimize bias through careful design but cannot fully eliminate selection and confounding biases like randomization can.
• B. Case reports are descriptive, single-patient accounts with no controls — highest risk of bias.
• C. Observational studies are prone to multiple forms of bias (selection, information, confounding).
• D. RANDOMIZATION is the most effective method to eliminate bias (particularly selection bias and confounding) in research. Random allocation of subjects to treatment groups ensures that both known and unknown confounding variables are equally distributed between groups, making the RCT the gold standard study design for minimizing bias.