# The SURVEYSELECT Procedure

#### Brewer’s PPS Method

Brewer’s method (METHOD=PPS_BREWER ) selects two units from each stratum, with probability proportional to size and without replacement. The selection probability for unit i in stratum h is . (Because selection probabilities cannot exceed 1, the relative size for each unit, , must not exceed .)

Brewer’s algorithm first selects a unit with probability

where

Then a second unit is selected from the remaining units with probability

where unit i is the first unit selected. The joint selection probability for units i and j in stratum h is

For more information, see Cochran (1977, pp. 261–263) and Brewer (1963). Brewer’s method yields the same selection probabilities and joint selection probabilities as Durbin’s method (Cochran 1977; Durbin 1967).