The SURVEYREG Procedure

STRATA Statement

STRATA variables </ options>;

The STRATA statement specifies variables that form the strata in a stratified sample design. The combinations of categories of STRATA variables define the strata in the sample.

If your sample design has stratification at multiple stages, you should identify only the first-stage strata in the STRATA statement. See the section Specification of Population Totals and Sampling Rates for more information.

If you provide replicate weights for BRR or jackknife variance estimation with the 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. The formatted values of the STRATA variables determine the levels. Thus, you can use formats to group values into levels. See the FORMAT procedure in the Base SAS Procedures Guide and the FORMAT statement and SAS formats in SAS Formats and Informats: Reference for more information.

When determining levels of a STRATA variable, an observation with missing values for this STRATA variable is excluded, unless you specify the MISSING option. For more information, see the section Missing Values.

You can use multiple STRATA statements to specify stratum variables.

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

LIST: displays a "Stratum Information" table, which includes values of the STRATA variables and the number of observations, number of clusters, population total, and sampling rate for each stratum. See the section Stratum Information for more details.
NOCOLLAPSE: prevents the procedure from collapsing (combining) strata that have only one sampling unit for the Taylor series variance estimation. By default, the procedure collapses strata that contain only one sampling unit for the Taylor series method. See the section Stratum Collapse for details.