topic Interaction not Working within Mixed MODEL in Statistical Procedures

Interaction not Working within Mixed MODEL

ALee — Mon, 03 Dec 2018 12:16:36 GMT

I am looking for some advice about interactions in SAS.

I am running a MIXED linear model with categorical and continuous variables. I am trying to determine if there is a quadratic relationship in the variable labeled cat. Normally I would put cat*cat or cat|cat to try to get an interaction. But when I run that code, my output still doesn't have an interaction as one of my type 3 tests of fixed effects. Is there a different symbol to try? Does anyone have any advice? My log shows no error messages, but there must be something wrong.

The code looks like this:

proc mixed data= allstock6 ;
class robotnr yr2 week2 cat;
model Meal= ages week1 cat week2 cat*cat/ddfm=SATTERTH s;
random pony week2(yr2) yr2;
repeated /type=ar(1) subject=pony;
lsmeans cat/diffs;
run;

Any help would be greatly appreciated!

Re: Interaction not Working within Mixed MODEL

StatsMan — Mon, 03 Dec 2018 13:30:27 GMT

If you want to treat CAT as a covariate, and model a linear and quadratic trend in CAT, then take CAT off the CLASS statement. You cannot really interact a categorical variable with itself.

Re: Interaction not Working within Mixed MODEL

ALee — Fri, 07 Dec 2018 07:32:48 GMT

Wow, I felt dumb once I realized what I was doing.

Thanks so much for the help!!