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
in stratum
equals
.
Brewer’s algorithm first selects a unit with probability
where
Then a second unit is selected from the remaining units with probability
where unit
is the first unit selected. The joint selection probability for units
and
in stratum
equals
Brewer’s method requires that the relative size
be less than 0.5 for all units. See Cochran (1977, pp. 261–263) and Brewer (1963) for details. Brewer’s method yields the same selection probabilities and joint selection probabilities as Durbin’s method. See Cochran (1977) and Durbin (1967) for details.