In order to use the covtest homogeneity option efficiently in GLIMMIX, you will need to specify something in a RANDOM statement and use the GROUP=option. Consider this:
proc glimmix data =dataset2(WHERE=( Abdominal_pain3=1);
class after_intervention Acuity2;
model ED_Completed_Length_of_Stay__Min=after_intervention Acuity2;
random _residual_/group=after_intervention;
covtest 'common variance' homogeneity; /* This does a likelihood ratio test for homogeneity */
lsmeans after_intervention;
contrast '0 vs 1' after_intervention -1 1;
;
run;
Now you may want to try various distributions for your dependent variable. If the data are truly non-normal, then it probably doesn't matter how large your dataset is. Fitting what you have now treats the residuals as normally distributed, so at least look at the plots of the studentized residuals. For a lot of time to event/waiting time data like this, a gamma distribution fits better than a normal.
SteveDenham
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