Blinding is a strategy used in clinical trial design. It is done by concealing group allocation from one or more parties involved in the trial- investigators, research staff, participants. Blinding is usually done after the randomization of trial subjects.

Why should we use blinding?

Using blinding in trials helps reduce the risk of intentional and unintentional bias such as performance and ascertainment bias, and increases the validity of the study.

Types of masking/blinding:

  • Single-blinded: Research subjects are unaware of their treatment assignment.
  • Double-blinded: The researchers and the subjects are unaware of the treatment assignments.

Source: Karanicolas, P. J., Farrokhyar, F., & Bhandari, M. (2010). Practical tips for surgical research: blinding: who, what, when, why, how?. Canadian journal of surgery. Journal canadien de chirurgie, 53(5), 345–348.