STRATA variables </ options> ;

The STRATA statement names the variables defining strata or representing matched or nested sets of individuals in a case-control study. Each STRATA variable can be either character or numeric, and the formatted values of the STRATA variables determine the levels. Thus, you can also use formats to group values into levels. See the discussion of the FORMAT procedure in the Base SAS Procedures Guide. At least one variable must be specified in order to invoke the stratified analysis. See the section Stratified Analysis for more information.

The following options can be specified after a slash (/):

INFO

displays the "Strata Information" table, which includes the stratum number, levels of the STRATA variables that define the stratum, total number of individuals, and counts for the two trait values that define cases and controls in each stratum. Since the number of strata can be very large, this table is displayed only on request.

MISSING

treats missing values (‘.’, ‘.A’,...,‘.Z’ for numeric variables and blanks for character variables) as valid STRATA variable values.