Blinding in a clinical trial reduces bias by concealing which information from participants about their assignment?

• A. It eliminates the need for randomization
• B. It eliminates bias by concealing treatment allocation
• C. It increases bias
• D. It has no effect on outcomes

Answer: (B)

Blinding reduces bias by concealing which treatment a participant has been assigned from the participant themselves, preventing expectations about the treatment from shaping how they report symptoms, adhere to the regimen, or behave during the trial. When participants don’t know whether they received the active intervention or a control, their perceptions and actions are less likely to be influenced by that knowledge, which helps keep comparisons between groups fair and the results more trustworthy.

The other ideas don’t fit because blinding isn’t about eliminating randomization—randomization is a separate process that assigns participants to groups. Blinding doesn’t increase bias; it reduces it. And blinding can affect outcomes by reducing biased influences, so saying it has no effect on outcomes isn’t accurate.