Rate ratios for glimmix poisson model

[analyst_work]

Hi, 

For a glimmix model,

• with a binomial distribution and logit function, you can specify the oddsratios option
• what can you specify for the poisson distribution and log link function?

I am trying to find an option that would output rate ratios. 

Thanks!

[StatDave · Accepted solution]

That can be done in PROC GENMOD as shown in the second half of this note. If you must use GLIMMIX, then you will need to include a STORE statement to save your model, then use the LSMEANS statement, as in the Note, in PROC PLM. For example:

     proc glimmix data=insure;
         class car age;
         model c = car age / dist=poisson link=log offset=ln;
         store glim;
         run;
     proc plm restore=glim;
         lsmeans age / ilink diff exp cl;
         run;

[analyst_work]

I have a follow-up question: Some of the exponentiated values and confidence interval limits from lsmeans are slightly different than the glimmix model output values. Is that expected and is there an explanation for this difference? Thanks!

[StatDave]

The values in the "Estimate" column in the LSMEANS table are linear combinations of model parameters and therefore are not in general going to equal any single parameter estimate in the rest of the GLIMMIX output. You can add the E option in the LSMEANS statement to see the coefficients of the linear combination used.