[R] SEM interaction
Jarrett Byrnes
byrnes at msi.ucsb.edu
Tue May 25 18:17:02 CEST 2010
Have you looked into multigroup analysis? Is that what you're after?
If so, you can do multigroup analysis in lavaan fairly easily or, if you're using the sem package, drop me a line. I have some scripts that will do multigroup analysis for an equal sample size.
See
http://faculty.chass.ncsu.edu/garson/PA765/structur.htm#multiplegroupanalysis
and
http://www.structuralequations.com/3.html
for some examples.
On May 25, 2010, at 8:38 AM, Anthony Dick wrote:
> Hello all,
>
> This is a general stats question--I realize it is an R help list, so tell me to go away if it is inappropriate.
>
> I have a 2 X 2 design, and I have specified four identical path models (one for each level of each factor). I want to test for an interaction at each path--essentially (A1 - A2) - (B1 - B2) != 0. I was thinking of computing a contrast for each path of interest, such that I compute the difference of the difference in the (non-standardized) path weights (as above), and then divide this by the pooled standard errors of the estimates (average of the standard errors).
>
> Does this seem statistically sound, or am I way off base? I typically compare path weights across two levels (e.g., age differences in a path weight for the same theoretical model) using the stacked model approach, but am not sure how to apply this to the interaction.
>
> Anthony
>
> --
> Anthony Steven Dick, Ph.D.
> Post-Doctoral Fellow
> Human Neuroscience Laboratory
> Department of Neurology
> The University of Chicago
> 5841 S. Maryland Ave. MC-2030
> Chicago, IL 60637
> Phone: (773)-834-7770
> Email: adick at uchicago.edu
> Web: http://home.uchicago.edu/~adick/
>
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