The process used in epidemiological studies and clinical trials in which the participants, investigators and/or assessors remain ignorant concerning the treatments which participants are receiving. The aim is to minimise observer bias, in which the assessor, the person making a measurement, have a prior interest or belief that one treatment is better than another, and therefore scores one better than another just because of that.
In a single blind study it is may be the participants who are blind to their allocations, or those who are making measurements of interest, the assessors.
In a double blind study, at a minimum both participants and assessors are blind to their allocations
