Medical Definition of Double-blind

Double-blind: Term used to described a study in which both the investigator or the participant are blind to (unaware of) the nature of the treatment the participant is receiving. Double-blind trials are thought to produce objective results, since the expectations of the researcher and the participant about the experimental treatment such as a drug do not affect the outcome. Also called double-masked. See also: Double-blinded study.

Source: MedTerms™ Medical Dictionary
http://www.medicinenet.com/script/main/art.asp?articlekey=38696
Last Editorial Review: 5/13/2016