You can specify a BY statement with PROC MULTTEST to obtain separate analyses on observations in groups defined by the BY variables. The variables are one or more variables in the input data set. When a BY statement appears, the procedure expects the input data set to be sorted in order of the BY variables. If your input data set is not sorted in ascending order, use one of the following alternatives:

• Sort the data by specifying the SORT procedure with a similar BY statement.

• Specify the BY statement option NOTSORTED or DESCENDING in the BY statement for the MULTTEST procedure. The NOTSORTED option does not mean that the data are unsorted but rather that the data are arranged in groups (according to values of the BY variables) and that these groups are not necessarily in alphabetical or increasing numeric order.

• Create an index on the BY variables specifying the DATASETS procedure (in Base SAS software).

Since sorting the data changes the order in which PROC MULTTEST reads observations, this can affect the sorting order for the levels of the CLASS variable if you have specified ORDER=DATA in the PROC MULTTEST statement. This, in turn, affects specifications in the CONTRAST statements.

For more information about the BY statement, see SAS Language Reference: Concepts. For more information about the DATASETS procedure, see the Base SAS Procedures Guide.