A double-blind study is one in which neither the person being treated nor the 
person evaluating the results of the treatment know who is getting which 
treatment.  That way you hope you eliminate the effects of expectations in 
both the patients (who may react differently if they know) and the evaluators 
(who may score differently if they know).
The recent study on the effect of color on the efficacy of medications shows 
just how important these effects can be.
Jerry Schwartz
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