study is one in which neither the subject
nor the investigator knows what treatment (if any) the subject
is receiving. Only after all the data are collected is the
investigator made aware of which subjects received which treatments.
The purpose of keeping the subject unaware
of the treatment is to minimize the psychological effects
of drug treatment. For example, a subject who knows she is
being given an experimental drug may expect beneficial results
and this may in fact increase the efficacy of the drug. (See
also: placebo effect.)
The purpose of keeping the investigator
unaware of the treatment is to minimize any inadvertent bias
by the investigator. For example, if the investigator believes
that a new drug is going to be highly effective in improving
memory, he may inadvertently tend to report data that support
his belief. By keeping the investigator unaware of treatment
until the end of the study, this source of potential bias
Well-designed research studies, particularly
of new drugs, usually employ randomization,
and double-blind techniques.
Further Reading: "Putting
Ginkgo to the Test"
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain