Blind experiment

A blind or blinded experiment is a test or experiment in where the experimenter does not know which treatment is given to a subject. The idea is to avoid bias which the experimenter might otherwise introduce.^[1] If both tester and subject are blinded, the trial is a double-blind trial.

Suppose consumers are asked to compare the tastes of different brands of a product. Obviously, the identities of the product should be hidden – otherwise consumers tend to prefer the brand they are familiar with. Similarly, when testing a pharmaceutical drug, both patients and experimenter should not know the dosage being given in each case.

The opposite of a blind trial is an open trial. The terms blind (adjective) or to blind (transitive verb) when used in this sense are figurative extensions of the literal idea of blindfolding someone.

1. ↑ Oxford English Dictionary, 2nd ed.