PROC GLIMMIX not giving AIC after adding random effect

[raheleh22]

Hi, 

I've been using Proc Glimmix to predict the effect of several predictor variables on my outcome where the distribution is negative binomial. for the purpose of model comparision when I run the following code I receive the AIC tests:

proc glimmix data=modelupdated;
class metcat(ref="2") age_new(ref="1") sexnum (ref="2") race(ref="2");
model Rate_12= age_new sexnum race metcat/ dist=nb link=log s;
run;

However when I add the random effect of counties, I do not receive the AIC in fit stati table in the output. 

proc glimmix data=modelupdated1;
class metcat(ref="2") age_new(ref="1") sexnum(ref="2") race(ref="2");
model Rate_12 = age_new sexnum race ave_uninsured metcat / dist=nb link=log s;
random intercept /type=un subject=fips_all_digit_num ;
run;

any thoughts on this and how I can get AIC becuse I need to compare the two different models vs eacg other. 

Thank you, 

[jiltao]

PROC GLIMMIX uses the Pseudo-likelihood estimation method to fit the model when there is a random effect, so no AIC is computed because no true likelihood is computed. To get the AIC, you can use a different estimation method, for example, method=quad or method=laplace in the PROC GLIMMIX statement.

Hope this helps,

Jill