What is blinding?

• A. Masking only to statisticians.
• B. Replacing all data with dummy values.
• C. Keeping treatment assignment unknown.
• D. Dual-armed trial.

Answer: (C)

Blinding means concealing which treatment a participant receives from those who are involved in the trial and could be influenced by that knowledge, so outcomes aren’t biased by expectations or differential care. Keeping the treatment assignment unknown is the core idea because it prevents placebo effects, observer bias, and biased assessments from shaping the results. Depending on who is kept unaware, blinding can be single, double, or triple in nature. The other options miss this essential concealment aspect: masking only to statisticians still leaves participants and investigators aware of treatment, which can bias results; replacing data with dummy values is data fabrication, not blinding; and having a dual-armed trial describes the number of groups, not the concealment of assignment.