Dennis-
Recently you said:
"The study is now a true double-blind (Did I miss
something?), but the control condition allows for more than one
interpretation of any differences observed."
The possibility of mulitiple interpretations _always_ exists regardless
of level of control. Even if you could rule out the warm/cold therapist
explanation someone could argue that there was some other variable (eye
colour, hair length, etc.) that differed between the groups & caused the
observed difference in the dependent variable. Since we cannot possibly
control
for _all_ possible variables we are forced to rely on Occam's Razor to
make a determination of which of the competing hypotheses is most
probable. This is, of course, not just a problem for double blind
studies but for all of scientific investigation.
BTW While we often tout double blind studies as the "gold standard" I
caution my students not to think that they are the only path to real
knowledge. After all, no one has done a double blind study on heart
transplants but I'm still pretty sure that they work. :)
-Don.
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Don Allen email: [EMAIL PROTECTED]
Dept. of Psychology voice: (604)-323-5871
Langara College fax: (604)-323-5555
100 W. 49th Ave.
Vancouver, B.C.
Canada, V5Y 2Z6
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