Apologies if this is duplicate question, but I can't find anything similar using search. I have a data set containing a continuous variable, isotope GFR (which should remain stable) measured at time 0 and at 4 months. There are three categorical outcome states assigned at four months (stable, improved, deteriorated). I'm trying to consider differences in baseline variable between outcome groups. Using scatter and Galton plots it appears there is a degree of regression to the mean in the measured variable. My thought on accounting for this is to use ANCOVA as below. However, my stats background is limited and I'd be very grateful for any comments as to the appropriateness of this method and / or advice on how to better handle this. Many thanks Jime PROC GLM DATA=Date; CLASS RESPONSE; MODEL GFR_0 =RESPONSE (GFR_4-GFR_0) ; LSMEANS RESPONSE / ADJUST=TUKEY PDIFF ; RUN;
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