Stephen Black wrote:
> Randomly assign subjects to either placebo therapy or cognitive
> therapy. So far, we have single-blind (subjects don't know which is
> the placebo). To make it double blind, have the outcome measures
> taken by independent interviewers or observers who don't know which
> treatment has been applied to which subjects. The interviewers would
> have to be cautioned not to ask any questions which could reveal which
> treatment the subjects had received, but this shouldn't be a problem.
>
> Bingo, double-blind study. QED.
Except that, since the experimenters themselves would know if they were
administering the placebo therapy or not, their interactions with the
subjects could be compromised by the knowledge and the results skewed. :(
In a medical double-blind experiment neither the subject _nor_ the
administering physician know whether they are in the experimental group or
the control group. That safeguard exists because doctors inadvertantly
communicated which group the subject was in through their interactions
(i.e., a doctor knowing a subject was receiving a placebo would
demonstrate less concern for "side effects" than one who knew the subject
was receiving the experimental substance). In a parallel psychological
experiment set up in the manner discussed above, the therapist would find
it virtually impossible to avoid some degree of contamination of the
experiment, if only through his/her lack of "authority" in the therapeutic
system. Try using a non-existant form of therapy with a client and see how
quickly the client begins to demonstrate lack of confidence in your
capability as a therapist (a critical component in the therapeutic
process). Thus, even if the observers were unaware of the nature of the
therapy, a true double-blind protocol wouldn't exist.
Sorry, Stephen. Back to the drawing board! :)
Rick
--
Rick Adams
[EMAIL PROTECTED]
Department of Social Sciences
Jackson Community College
2111 Emmons Rd.
Jackson, MI 49201
