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If you specify the ALLOC= option in the STRATA statement, PROC SURVEYSELECT allocates the total sample size among the strata according to the method that you request. PROC SURVEYSELECT provides proportional allocation (ALLOC=PROPORTIONAL ), optimal allocation (ALLOC=OPTIMAL ), and Neyman allocation (ALLOC=NEYMAN ). For more information about these allocation methods, see Lohr (2010), Kish (1965), and Cochran (1977). You can also directly provide the allocation proportions by using the ALLOC=(values) option or the ALLOC=SAS-data-set option. Then PROC SURVEYSELECT allocates the sample size among the strata according to the proportions that you provide. Allocation proportions are the relative stratum sample sizes, , where is the sample size for stratum h and n is the total sample size.

You can use the SAMPSIZE=n option in the PROC SURVEYSELECT statement to specify the total sample size to allocate among the strata. Or you can specify the required margin of error in the MARGIN= option in the STRATA statement, and PROC SURVEYSELECT computes the stratum sample sizes necessary to achieve that margin of error for the allocation method that you request. For more information, see the section Specifying the Margin of Error.