STRATA variables ;
The STRATA statement names one or more variables that form the strata in a stratified sample design. The combinations of levels of STRATA variables define the strata in the sample, where strata are nonoverlapping subgroups that were sampled independently.
If your sample design has stratification at multiple stages, you should identify only the first-stage strata in the STRATA statement. For more information, see the section Specifying the Sample Design.
If you provide replicate weights in a REPWEIGHTS statement, you do not need to use a STRATA statement.
The STRATA variables are one or more variables in the DATA= input data set. These variables can be either character or numeric, but PROC SURVEYIMPUTE treats them as categorical variables. The formatted values of the STRATA variables determine the STRATA variable levels. Thus, you can use formats to group values into levels. For more information, see the discussion of the FORMAT procedure in the Base SAS Procedures Guide and the discussions of the FORMAT statement and SAS formats in the SAS Formats and Informats: Reference.