SAS Defaults for Proc Freq in CMH DIF analysis

[Jaime2]

Hi All,

This seems like a silly question but I cannot figure out what default scheme is used to assign the "reference" and "focal group" in a typical differential item functioning analysis using PROC FREQ. 

My code is : 

proc freq data=mydata;
tables stratum*gender*item&i./CMH noprint;
output out=item&i. MHCHI COMOR CMH ; run;

My gender variable is not dummy coded and has values = Male , Female. 

Would SAS use Females as the reference group since F comes before M, alphabetically? There has to be a rule documented someplace but I cannot find it. Of course my results are meaningless without knowing this. 

Thanks for any tips or links. 

[Watts · Accepted solution]

The ORDER= option in the PROC FREQ statement specifies the order of the variable levels.

The default is ORDER=INTERNAL, which orders the levels by unformatted values ('Female' before 'Male').