A clinical trial design in which neither the patient nor the study staff know which patients are receiving the experimental drug and which are receiving a placebo (or another therapy).

See Blinding or masking

In order to control for experimenter effects and demand characteristics, neither the subjects nor the experimenter knows which group of subjects has received which experimental treatment until after t [..]

A type of clinical trial in which two or more parties involved with the trial (usually the participants and researchers) do not know which participants are receiving the experimental intervention and which participants are receiving the control (a standard intervention that is considered effective). See Related Term(s): Clinical Trial, Control Arm, [..]

A controlled experiment in which neither the patient nor the physician knows whether the patient is getting one or another drug or dose.

A study in which at least two separate groups receive the experimental medication or procedure at different times, with neither group being made aware of when the experimental treatment or procedure has been given. The purpose of a double-blind study is to eliminate the risk of prejudgment by the participants, which could distort the results. Doubl [..]

If the statistical analysis is also done in ignorance of the group to which subjects belong, the study is sometimes described as triple blind