The CLASS statement is required unless the INPVALUES= option is specified. The CLASS statement specifies a single variable (character or numeric) used to identify the groups for the analysis. For example, if the variable Treatment defines different levels of a treatment that you want to compare, then you would specify the following statements:

   class Treatment;

The CLASS variable can be either character or numeric. By default, its levels are determined from entire formatted values. Prior to SAS 9, class levels were determined by using no more than the first 16 characters of the formatted values. If you want to revert to this previous behavior, you can specify the TRUNCATE option in the CLASS statement. In any case, you can use formats to group values into levels. See the discussion of the FORMAT procedure in the Base SAS Procedures Guide and the discussions of the FORMAT statement and SAS formats in SAS Language Reference: Dictionary. You can adjust the order of CLASS variable levels with the ORDER= option in the PROC MULTTEST statement. You need to be aware of the order when using the CONTRAST statement, and you should check the "Contrast Coefficients" table to verify that it is suitable.

You can specify the following option in the CLASS statement after a slash(/):