I'm trying to analyze count variables (poisson distribution)  with repeated measures using proc glinmix. I have observation of behavior of animals  observed during 3 days after applying a treatment. In this case treatment is "environmental enrichment"  for calves to improve their behavior (two classes, yes or no). Activities (y in my model) is measured by time doing certain activity. I have many "0" time observation in my file, then I'm trying to analyze with GLINMIX using Poisson distribution. Model i'm using is:   proc glinmixed data=b method=quad; class treatment day id;                 *id is the identification o animal *; model eating = treatment + day / link=log s dist=poisson;   *eating is measured in minutes  *; subject = id; lsmeans  treatment; run;   My doubt is: 1) how could I interpret least square means for treatment?; 2) in the case I have many "zero" values for y, sometimes the least square means is negative. Is it correct?   Many thanks, Lenira     ... View more