The STRATA statement names variables that identify the first-stage 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 specify only the first-stage strata in the STRATA statement. See the section Specifying the Sample Design for more information.

If you provide replicate weights for BRR or jackknife variance estimation with a REPWEIGHTS statement, you do not need to specify 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 the procedure 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. 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.

Note that an observation is excluded from the analysis if it has a missing value for any STRATA variable unless you specify the MISSING option in the PROC SURVEYFREQ statement. See the section Missing Values for more information.

You can use multiple STRATA statements to specify STRATA variables. The procedure uses variables from all STRATA statements to define strata.

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