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Re: st: xtmixed versus spss mixed; random intercept only model


From   Philip Ender <ender97@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: xtmixed versus spss mixed; random intercept only model
Date   Thu, 23 Sep 2010 12:44:18 -0700

I'm trying to understand why Stata and SPSS provide slightly (or not
so much) different results when analyzing the same data with the same
(I believe) model.  I'm trying to tie out the two software results,
beginning with a very SIMPLE model, then working up to what I'd really
like to do.  Since I've already ran into differences on a very simple
model, I thought to ping the list to see if I'm going down the wrong
path??

...

--------------------------------

Robert,

Try rerunning the -xtmixed- command changing the reference group for
trmt.  If the groups are unbalanced than estimates for the intercept,
continuous variable and interaction can be different.  Try this code:

xtmixed y c.time##ib1.trmt||subj:, cov(id)

Phil
-- 
Phil Ender
UCLA Statistical Consulting Group
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