FREQ variable;
The FREQ statement names a numeric variable that contains the frequency of occurrence of each observation. If you use a FREQ statement, PROC SURVEYSELECT assumes that an observation represents n observations, where n is the value of the FREQ variable for the observation. The FREQ statement is not available when you specify a SAMPLINGUNIT statement.
The FREQ statement is available only for sample allocation when no sample is selected, which you can request by specifying the ALLOC= and NOSAMPLE options in the STRATA statement. The ALLOC= option requests allocation of the total sample size among the strata, and the NOSAMPLE option requests that no sample be selected after allocation. When you specify the NOSAMPLE option, the procedure computes stratum sample sizes according to the allocation method that you request, but does not select the sample. For more information, see the section Sample Size Allocation.
The sum of the FREQ variable values (frequencies) represents the total number of sampling units. The sum of the frequencies in a stratum represents the total number of sampling units in the stratum. When you use a FREQ statement, the sample size allocation is based on the expanded total and stratum frequencies.
Values of the FREQ variable must be nonmissing and nonnegative. If a value of the FREQ variable is 0, PROC SURVEYSELECT ignores the observation. If a value of the FREQ variable is not an integer, PROC SURVEYSELECT uses only the integer portion as the frequency of the observation.