The MULTTEST Procedure

CLASS Statement

CLASS variable </ TRUNCATE>;

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, class levels are determined from the entire set of formatted values of the CLASS variable. The order of the class levels used by PROC MULTTEST corresponds to the order of their formatted values; this order can be changed with the ORDER= option in the PROC MULTTEST statement.

Note: Prior to SAS 9, class levels were determined by using no more than the first 16 characters of the formatted values. 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 Formats and Informats: Reference. 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 (/):

TRUNCATE: specifies that class levels should be determined by using only up to the first 16 characters of the formatted values of CLASS variables. When formatted values are longer than 16 characters, you can use this option to revert to the levels as determined in releases prior to SAS 9.