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st: Need to Determine an Intervention Effect using xtmixed


From   "Elizabeth Prezio" <eaprezio@sbcglobal.net>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Need to Determine an Intervention Effect using xtmixed
Date   Tue, 4 Sep 2012 16:58:14 -0500

I am using xtmixed to evaluate panel data. There are two groups. I have
repeated measures for my outcome of interest (hemoglobin A1c at baseline,
3,6,9, and 12 months). I can get adjusted means for HbA1c using margins, but
I am at a loss to calculate an "intervention effect". I need a between group
comparison. 


. xtmixed test i.patgrp##i.time duration blmeds medchange hba1_bl || id:

                I get expected output.

Margins i.patgrp##i.time, at means post

                I get adjusted means

pwcompare i.patgrp#i.time
                
                I get pairwise comparisons with 95% CI

Then I used nnmeans and got numbers which did not fly with my dissertation
committee. This provided an adjusted treatment effect.which I was happy
about, but apparently this is not correct.

None of my committee members use STATA. 

I need some sort of "intervention effect" comparing the adjusted HbA1c
(test) values over  12 months between the intervention and control groups. I
need 95% CI and a P-value.


Any help would be greatly appreciated.

Beth 



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