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st: cluster sampling with PPS

From   Gretchen Caspary <>
To   Statalist <>
Subject   st: cluster sampling with PPS
Date   Tue, 17 Sep 2002 17:33:45 -0700

This regards the generation of a random sample.

I have a data set with 4,000 observations, containing 480 unique zip codes.
I want to generate a random sample with 30 zip codes.

I've been told (by a SAS user) that the technique I should use is called "2
stage cluster sampling" or something similar, in which the first stage is
"probability proportionate to size (PPS)."  That is, I want to be sure that
those zip codes that have more observations are proportionately more likely
to be chosen for the sample of 30 zip codes.

I have looked on-line, and found the "sample2" syntax, but that only allows
a percentage sampling, and does not appear to do PPS in the first stage(?).

Thanks for any suggestions

Gretchen Caspary

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