04-06-2015 12:11 PM
Hi SAS Community,
I have a quick question about proc glimmix. When using proc nlmixed, the analyst specifies the distribution of the random effects. Is there any such option with proc glimmix? I could not see. If there is no such option in proc glimmix, can anyone please suggest a way to specify a random effects distribution different from the normal distribution? Thanks.
04-06-2015 03:33 PM
The random effects can only have a normal distribution in glimmix (of course, the response variable can have any of the conditional distributions in the exponential family). Random effects must also be normal in nlmixed (no other ones allowed). With nlmixed, there are some tricks to get other random-effect distributions (I have tried some), but these are very tricky to use, and often do not converge. Fortunately, most model fitting results are not too dependent on the normal assumption for the random effects.