On 26 May 2001 03:50:32 GMT, Elliot Cramer <[EMAIL PROTECTED]>
wrote:
> Rich Ulrich <[EMAIL PROTECTED]> wrote:
> : - I was a bit surprised by the newspaper coverage. I tend to
> : forget that most people, including scientists, do *not* blame
> : regression-to-the-mean, as the FIRST suspicious cause
> : whenever there is a pre-post design: because they have
> : scarce heard of it.
>
> I don't see how RTM can explain the average change in a prepost design
- explanation: whole experiment is conducted on patients
who are at their *worst* because the flare-up is what sent
them to a doctor. Sorry; I might have been more complete
there. All the pre-post studies in psychiatric intervention
(where I work) have this as something to watch for.
I guess I could have said, "first suspicious cause *of
selective improvement* in any pre-post design."
> those above the pre population mean will tend to be closer to the post
> population mean but this doesn't say anything about the average
> change. Any depression study is apt to show both a placebo AND a no
> treatment effect after 6 weeks
- I'm not sure what that last phrase means... "both ...."
30% or so of acutely depressed patients will get quite a bit better.
In psychiatry, I think we have called some effects "placebo"
even when we know that it is not a very good word.
The experience of being in a research trial, by the way, seems
to produce a placebo effect, according to what people have told me.
(I think that careful scientists attribute that one to the extra time
and attention given to those subjects.)
--
Rich Ulrich, [EMAIL PROTECTED]
http://www.pitt.edu/~wpilib/index.html
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