Each observation is a discrete count representing the percentage of ablation surgeries performed per year for each group (NICM and ICM). You percent response is an aggregated binary (ablative surgery or not) response. If you have the counts of the number of ablative surgeries and the total number of surgeries making up the percentages, you would specify them in the MODEL statement using events/trials syntax and specify that the distribution is binomial:   model Nablative/Ntotal=disease yearidx yearidx*disease / dist=binomial noint;   ... View more