What is a blind trial?

• A. Where researchers know all assignments
• B. Where patients don't know if they have the drug or the placebo
• C. Where neither patients nor researchers know
• D. Where only researchers know

Answer: (B)

Blinding reduces bias in trials by keeping treatment details hidden from those involved. A blind trial means the people receiving the treatment do not know whether they are getting the active drug or the placebo. This prevents their beliefs or expectations from influencing how they report symptoms or respond to the treatment. If only the participants are unaware, that’s a single-blind setup; if no one knows, that’s a double-blind setup. The key idea is protecting outcomes from expectations, and the option describing participants not knowing fits that best.