double-blind study

An experimental protocol used when studying the effects of an experimental treatment. One group is given the experimental treatment (e.g. a certain drug), while the other group receives a control treatment (e.g. a placebo). In a double-blind study neither the investigator nor the subjects know who is receiving the experimental or control treatments.

In drug tests a double-blind study is a study in which neither the investigator administering the drug nor the subject taking it knows if the patient is receiving the experimental drug or a neutral substitute called a placebo. In this manner, bias, either on the part of the administrator or the subject, can be eliminated from the study.

A study of the effects of a specific agent in which neither the administrator nor the recipient, at the time of administration, knows whether the active or an inert substance is given.