The class statement with PROC MDC

[Demographer]

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.

[Rick_SAS]

Could you share the syntax and output? Perhaps on a SASHELP or a simulated data set so we can all see the problem?

[Demographer]

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.

proc mdc;

class=a;

model y = a b c/

type=mixedlogit nchoice=10 mixed=(normalparm=a);

id id;

run;

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.

[Rick_SAS]

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.

[Demographer]

Those commands are not supported by PROC MDC. See there:

[Rick_SAS]

I apologize. I'd go to tech support with this one.  The documentation doesn't  even mention the syntax you are using.

[Demographer]

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.