Double blind trials minimize bias by ensuring which groups are unaware of treatment assignment?

• A. Only patients
• B. Both patients and researchers
• C. Only researchers
• D. Neither

Answer: (B)

Blinding helps prevent expectations from shaping study results. In a double-blind trial, both the participants and those administering or assessing the treatment do not know which treatment each person received. This stops patients’ beliefs about what they’re taking from influencing their reported outcomes and stops researchers or outcome assessors from unconsciously treating groups differently or rating symptoms differently based on assignment. By keeping both sides unaware, comparisons between treatments reflect the true effect of the intervention rather than biases introduced by knowledge of the treatment. If only one group were blinded, bias could still creep in—patients might report differently if they know their treatment, or researchers might assess outcomes differently if they know who received which treatment. If neither group is blinded, biases would be even more likely to distort results.