At 02:26 PM 9/26/01 -0500, Burke Johnson wrote:
> >From my understanding, there are three popular ways to analyze the
> following design (let's call it the pretest-posttest control-group design):
>
>R Pretest Treatment Posttest
>R Pretest Control Posttest
if random assignment has occurred ... then, we assume and we had better
find that the means on the pretest are close to being the same ... if we
don't, then we wonder about random assignment (which creates a mess)
anyway, i digress ...
what i would do is to do a simple t test on the difference in posttest
means and, if you find something here ... then that means that treatment
"changed" differentially compared to control
if that happens, why do anything more complicated? has not the answer to
your main question been found?
now, what if you don't ... then, maybe something a bit more complex is
appropriate
IMHO
_________________________________________________________
dennis roberts, educational psychology, penn state university
208 cedar, AC 8148632401, mailto:[EMAIL PROTECTED]
http://roberts.ed.psu.edu/users/droberts/drober~1.htm
=================================================================
Instructions for joining and leaving this list and remarks about
the problem of INAPPROPRIATE MESSAGES are available at
http://jse.stat.ncsu.edu/
=================================================================