CLASS variables;
The required CLASS statement specifies the following input variables, which are used as classification variables:
the variable to use as the treatment indicator in the PSDATA, PSMODEL, and EWEIGHT statements
the classification covariates in the logistic model in the PSMODEL statement
the classification variables that you specify in the VAR= option in the ASSESS statement
If you specify a PSMODEL statement, the CLASS statement must precede the PSMODEL statement. Classification variables can be either character or numeric.