What Is Blinding?

Looking for the full method? Read the detailed guide: Randomized Controlled Trials Explained.

Blinding (also called masking) means keeping people unaware of which intervention a participant received, to reduce bias in how outcomes are experienced, delivered or assessed. Those who may be blinded include participants, care providers, outcome assessors and analysts.

Example

Invented for teaching: In a drug trial, identical-looking tablets are used so that neither participants nor clinicians know who received the active drug. An outcome assessor who does not know group allocation rates the patients' symptoms.

Common misunderstanding

"Double-blind" is not a single standard definition, so reports should say who was blinded. Blinding is different from allocation concealment: blinding occurs after allocation, while concealment protects the assignment process beforehand. Some interventions, such as surgery, cannot easily be blinded for participants.

Learn more

See Randomized Controlled Trials Explained.

This page is general educational information about research methods. It is not medical, legal or regulatory advice; follow your institution's ethics board and your target journal's instructions.