08-07-2015 01:49 PM
I think there is a problem with the class statement using proc MDC (type=mixedlogit). In the results, there is a parameter for the reference value, which is a non-sense. Moreover, this parameter has no standard error. I really don't get why. I know I could just create dummy variables, but I want to be sure that it's not another problem. Thanks.
08-07-2015 03:45 PM
I work in a secure lab so I can't copy/paste the syntax. The syntax was basic, such as:
Suppose variable "a" has 3 categories.
model y = a b c/
type=mixedlogit nchoice=10 mixed=(normalparm=a);
The output is normal for the other variables. The only major bug is that there is a parameter for the reference value of the variable "a" and that parameter doesn't have standard error.
08-07-2015 04:21 PM
Your syntax doesn't correctly specify the reference parameterization. You need to say
class a(ref='1') / param=ref;
where '1' should be replaced by whatever level you want to use for the reference level.
08-07-2015 05:34 PM
I think the documentation is not up to date. The class statement with proc MDC works with SAS 9.4 (with the bug mentionned above), but is not supported with SAS 9.1.