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st: question: an example of xtmixed: testing differences between groups at specific times
From
"Sun, Wensheng" <[email protected]>
To
"[email protected]" <[email protected]>
Subject
st: question: an example of xtmixed: testing differences between groups at specific times
Date
Tue, 8 Jan 2013 19:49:35 -0600
Hi,
I am using –xtmixed- on a longitudinal study with planned measurements at 0, 6, 12 and 24 months, but very few follow-up measurements at the planned time. I have fitted the model and need to evaluate changes from baseline and also differences between two treatment groups at exactly 6, 12 and 24 months. The –xtmixed- followed by –margins- gives margins and standard error at each time. How do I compare them? I am using Stata 12 for Windows.
An example of that in public shared data should be
. webuse childweight
. xtmixed weight c.age##i.girl || id: age, cov(uns) res(ind) mle variance
. margin girl, at(age=(0.5 1 1.5 2))
What STATA commands should I use if I want to compare the weight between boys and girls at age of 0.5, 1, 1.5, and 2? and How should I compare changes from .5-year to 1 or 1.5 or 2 in girls and boys?
Thank you very much!
Carol
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