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If you specify the option METHOD=PPS_SYS, PROC SURVEYSELECT selects units by systematic random sampling with probability proportional to size. Systematic sampling selects units at a fixed interval ...

If you specify the option METHOD=PPS, PROC SURVEYSELECT selects units with probability proportional to size and without replacement. The selection probability for unit i in stratum h equals n h Z hi .

This is a preview. Log in through your library . Abstract The nested case—control design is frequently used to evaluate exposures and health outcomes within the confines of a cohort study. When ...