PROC GLIMMIX and MIXED basic questions

BlueNose — Mon, 10 Feb 2014 13:32:29 GMT

Hello all,

I have some basic questions regarding PROC GLIMMIX and PROC MIXED, and probably other mixed models related PROC's.

Assume that I have an outcome variable Y, continuous, and a treatment variable X with 2 levels. Let's also say that every subject in the analysis contributes 3 data points (can be 3 treatments in one person, or students within schools).

If I write this code:

proc mixed data = ....;

class SubjID;

model Y = X / solution cl;

[random statement]

run;

what is the difference between:

random SubjID;

random intercept / subject = SubjID;

and let's say (if it's a legal statement):

random Treatment / subject = SubjID;

I tried it on a small data set and the first two options gave me identical results. This question of course is relevant also for glimmix with a dist = binary.

And one more question, if I have this scenario, and I run a PROC MIXED once with random statement and once with REPEATED, and the results are very similar and leading to the same conclusions, how can I choose if to use R side or G side covariance ?

Thank you !

Re: PROC GLIMMIX and MIXED basic questions

SteveDenham — Fri, 14 Feb 2014 19:14:22 GMT

A really valuable source is SAS for Mixed Models, 2nd ed. by Littell et al. I can't imagine working with SAS and mixed models without having this available.

And it will answer every one of your questions that you posed.

Steve Denham

topic Re: PROC GLIMMIX and MIXED basic questions in Statistical Procedures

PROC GLIMMIX and MIXED basic questions

Re: PROC GLIMMIX and MIXED basic questions