here are a few urls i found at http://www.google.com
how good they are ... i leave that up to you
http://web.uccs.edu/lbecker/Psy590/gainscore.htm
http://www.ulib.org/webRoot/Books/National_Academy_Press_Books/motor_performance/cover001.htm
http://trochim.human.cornell.edu/courses/hss292/data-b.htm
http://espse.ed.psu.edu/espse/hale/507Mat/Chapt13/Chapt13.html
oh ... my boss came up in the search!!!
http://web.uccs.edu/lbecker/Psy590/blocking.htm
in design terms ... say you have pre scores ... take top 1/4 and bottom 1/4
... then you have a pre column of data that fit in
predata post data
high post scores
scores
low post scores
scores
then you do a two way anova ... with pre/post being a within Ss factor ...
and high group versus low group being a between Ss factor ... (it is like a
blocking factor) ...
there are means in each cell ... and what your student is hypothesizing is
an INTERACTION between the two factors ... with a greater difference
between the means for pre (high and low) than between the means on the
post (between the high and low groups)
| X
| X
| o
|
| o
|------------------
pre post
both groups gain (high is the X group and o is the low group) but, low
gains relatively more
At 12:55 PM 1/24/01 -0800, Dale Berger 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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