CLUSTER Statement

  • CLUSTER variables;

The CLUSTER statement names variables that identify the first-stage clusters in a clustered sample design. First-stage clusters are also known as primary sampling units (PSUs). The combinations of categories of CLUSTER variables define the clusters in the sample. If you also use the STRATA statement, clusters are nested within strata.

If your sample design has clustering at multiple stages, you should specify only the first-stage clusters (PSUs) in the CLUSTER statement. For more information, see the section Specifying the Sample Design.

If you use a REPWEIGHTS statement to provide replicate weights for the BRR or jackknife variance estimation method, you do not need to use a CLUSTER statement.

The CLUSTER 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 CLUSTER variables determine the cluster 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 SAS Formats and Informats: Reference.

You can use multiple CLUSTER statements to specify CLUSTER variables. PROC SURVEYIMPUTE uses variables from all CLUSTER statements to create clusters.