Double-Blind Study
Definition
A study in which participants and relevant investigators do not know the assigned intervention during the blinded part of the trial.
By PurePeptideHub Editorial Team · Updated . Educational source review; independent clinical review pending.
What blinding protects against
Expectations can influence symptom reporting, the care people receive and the way outcomes are assessed. Blinding tries to reduce those influences. A useful methods section identifies exactly who was masked: participants, treating staff, outcome assessors or analysts. The phrase double-blind alone may leave those roles unclear.
References: [1]
Example: a pain outcome
In a hypothetical trial of pain relief, participants receive similar-looking preparations and assessors use the same questionnaire. Concealing assignment can reduce expectation effects. If distinctive side effects reveal the intervention, the mask may be less effective even though the trial was designed to be blinded.
Different from randomization
Randomization concerns how participants are assigned; blinding concerns who knows the assignment. Placebo control describes the comparator. A study can have one feature without the others. Also check missing data, prespecified outcomes and the size of the effect before judging the result.