Blind Experiment:

A form of experiment in which the participants are, to some degree, kept ignorant of the nature and doses of materials administered as specific parts of the experiment. The purpose of the device is, obviously to prevent a prejudiced interpretation of the drug effects observed, and to prevent a presumed knowledge of effects to be expected from influencing the kinds of effects manifested by a subject. Blind experiments are not limited in use to experiments involving only human subjects. Needless to say, both experimenters and subjects may have general knowledge of the purpose, materials and design of the experiment; their ignorance is limited to the nature of individual drug administrations.

In a “single-blind” experiment, one participant – usually the subject – is left uninformed. In a “double-blind” experiment two participants – usually the subject and observer – are uninformed, and in a “triple-blind” experiment the subject, the observer, and the person responsible for the actual administration of the drug are left unaware of the nature of the material administered.

In clinical experimentation, particularly, the use of blind experimentation is frequently associated with the use of dummy or placebo medication as part of the experimental design, and the use of a “cross-over” experimental design.