the general problem you face is common to most studies like this ... UNLESS
there is a whopping mean change AND, the scores on the post have
considerably more variance than the pre ... have a look at
if not ... then you get a negative r between pre and gain ...
http://roberts.ed.psu.edu/users/droberts/5501.htm
question 1 is whether the program had any general impact ... and of course,
a one group pre and post design will NOT answer that ... since there is NO
comparison group who did NOT get the program ...
that is problem 1
problem 2 is that if the two distributions are roughly the same ... in
spread and not much difference in means ... then it is like a test retest
reliability situation and ... highs get relatively lower and lows get
relatively higher
this is problem 2
perhaps if you could present a bit of the data in some table form ... we
could make more substantive comments but ... the hypothesis he has is
confounded by regression to the mean ... and you have treatment and RTM in
this group ... and no group with ONLY RTM ...
At 12:55 PM 1/24/01 -0800, you wrote:
>Dear Colleagues,
>
>A student is evaluating a summer program for junior high students. One of
>the goals was to raise 'self esteem.' Measures were taken before the
>program, at the end, and a month later. He expected that the program would
>be most effective for those who entered with especially low self esteem. He
>divided the students into quartiles based on the pretest and compared these
>subgroups on change. He found that his hypothesis was supported - there was
>greatest positive change for those who entered in the lowest quartile.
>
>However, further examination showed a clear 'regression toward the mean'
>effect, including a small negative change for the group that entered in the
>highest quartile. (The test does not have great reliability.)
>
>Question: How should he analyze these data?
>
>I would appreciate some discussion of this situation. Thank you.
>
>Dale Berger
>
>
>
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_________________________________________________________
dennis roberts, educational psychology, penn state university
208 cedar, AC 8148632401, mailto:[EMAIL PROTECTED]
http://roberts.ed.psu.edu/users/droberts/drober~1.htm
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