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Re: st: Xtmixed specification for rmANOVA with 2 within-subject factors


From   "Airey, David C" <david.airey@vanderbilt.edu>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Xtmixed specification for rmANOVA with 2 within-subject factors
Date   Wed, 6 Apr 2011 09:35:35 -0500

.

> Hi Dave,
> 
> Thanks for the response!
> 
> And thanks for the tip on anovalator! I've recently started using it, and very much enjoy it!
> 
> I do have the book you mention, and have found it particularly useful in expanding my understanding of LMMs. 
> 
> I'm still finding myself having a remaining issue though.
> 
> In the book, the rat-brain example would suggest that with two within-subject factors a model such as this would suffice : 
> 
> xtmixed y  b##c | s:, var
> 
> --
> 
> I was mainly then confused by the UCLA page here:
> 
> 
> http://www.ats.ucla.edu/stat/stata/faq/margins_mixed_anova.htm
> 
> 
> Where for a split-plot design with two within-subject factors (along with a between-subject factor) the authors use the crossed-random factor model:
> 
> e.g.  xtmixed y a##b##c || _all: R.bs || _all: R.cs || _all: R.bcs || s:, var
> 
> I'm mainly confused as to why in this instance of a split-plot (with 2 within subject factors), but neither in the rat-brain totally within-subjects example from the book nor the first split-plot model presented on the UCLA page (1 between subject factor, 1 witihin-subject factor), are the the within-subject factors now considered crossed random-effects.
> 
> I haven't been able to reconcile the different approaches, even after reading the chapter from the book.
> 
> Thanks again!
> Jared

I think this has come up before on Statalist, and has to do with conceptualization of the rmANOVA model.

<http://www.stata.com/statalist/archive/2010-03/msg01340.html>

It is a good question for the authors of that book, or tech-support at Stata Corp.

-Dave


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