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st: Mixed models for repeated measures


From   Avi Zakai <aviz@trdf.technion.ac.il>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: Mixed models for repeated measures
Date   Fri, 5 Oct 2012 21:40:10 +0000

Hello



I have data for the comparison of a new treatment for eye disease versus two control groups.



My response (Y) is an ordinal variable with 8 levels. I have the group variable (X), and for every subject (S), I have two measurments, representing the two eyes !



I need to run a model to compare the different treatments, while taking into account the inner correlation within a subject, and I need to do it with STATA 12.



I was thinking about mixed models, however no matter what I tried, I got error messages. I would like to ask, what is the syntax I need to write in order to run a mixed model of Y=bX+e where e~N(0,R). The correlation between the eyes is 0.6, there is no structure since it's only 2 measurments. This model assumes normallity, it's the best I could think of, is there a better model in STATA for my ordinal scale ?



Thank you !

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