Re: Non-Equivalent Control Groups Design/ Quasi-Experimental Design

Posted by Bruce Weaver on Jul 15, 2016; 12:40pm
URL: http://spssx-discussion.165.s1.nabble.com/Non-Equivalent-Control-Groups-Design-Quasi-Experimental-Design-tp5732723p5732745.html

The diagram in the original post shows (in an somewhat unconventional way) a 3 (weight groups) x 3 (treatments) table with 9 Ss per cell, so N = 81 in total.  I must confess that I haven't followed this thread that closely, but it seems to me the main question boils down to whether the 27 in each weight group were randomly allocated to the 3 treatments.  

Kat, apologies if I missed this earlier in the thread, but how did you allocate the 27 Ss within each weight group to the three treatments?  

HTH.

Mike wrote

If collecting the data is not too difficult, I would suggest
replicating the experiment -- we are talking about N=27,
right?  The key thing would be randomize the people in
the blocks across the images, following the example of
Allan Edwards that I provided earlier.  The analysis would
be rather straightforward from there.  Moreover, you could
compare the results from the first experiment to the second
experiment to see how much of a difference the randomization
makes in the results.

It is possible that a source like Kirk or some other researcher
has analyzed a design like you have now and has figured out
a way to make sense of the data but this will entail a search
of the literature and evaluation of the methods.  This could take
a fair amount of time unless someone knows for sure that there
is (or there is not) another way to analyze the data.

The decision I think you have to make is which of the above
options will take less time to do.

-Mike Palij
New York University