WordNet (r) 3.0 (2006):

double-blind experiment
    n 1: an experimental procedure in which neither the subjects of
         the experiment nor the persons administering the experiment
         know the critical aspects of the experiment; "a double-
         blind procedure is used to guard against both experimenter
         bias and placebo effects" [syn: double-blind procedure,
         double-blind experiment, double-blind study]