I run a mixed model according to the PROC MIXED step in SAS. My code is like this below: proc mixed data=inds;
class subject arm(ref='C组（对照组）') ;
model aval =base arm avisitn arm*avisitn /s ;
random subject ;
repeated / subject=subject ;
lsmeans arm / diff cl at avisitn=0;
lsmeans arm / diff cl at avisitn=1;
lsmeans arm / diff cl at avisitn=2;
ods output diffs=diff ;
run; Then I change the variable in the model option at the left side of the equation like this: proc mixed data=inds;
class subject arm(ref='C组（对照组）') ;
model chg =base arm avisitn arm*avisitn /s;
random subject ;
repeated / subject=subject ;
/* lsmeans arm / pdiff cl at avisitn=0;*/
lsmeans arm / pdiff cl at avisitn=1;
lsmeans arm / pdiff cl at avisitn=2;
ods output diffs=diff1 ;
run; I just change the variable from the value at each time point to the change from baseline. Then I find that the Differences of Least Squares Means is the same. I do not know how this works. Can anyone tell me why? A explanation from the model and a suggestion from the code so that I can see why I get the same results.
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