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/
=================================================================

Reply via email to