Blinding

Blinding (also called masking) hides treatment assignment from one or more parties in a trial: participants, the clinicians delivering care, the people measuring outcomes, and sometimes the statisticians. It matters because knowing who got the active treatment can change behavior and judgment. Unblinded participants may report symptoms differently, and unblinded assessors may rate subjective outcomes more favorably for the treatment they expect to work. When reading a study, look for who exactly was blinded, not just the loose label double-blind, and consider whether the outcome is subjective (pain, mood) where blinding matters most, or hard and objective (death) where it matters less. Check whether blinding could have been broken by obvious side effects. Example: in a pain drug trial, blinded participants and assessors keep expectation from inflating the apparent benefit. Ask whether the most bias-prone measurements were protected by blinding.