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st: Clustering of secondary units in sampling design


From   Ángel Rodríguez Laso <angelrlaso@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Clustering of secondary units in sampling design
Date   Mon, 5 Oct 2009 16:50:52 +0200

Dear Statalisters,

When analysing multistage survey data, Stata only needs a Primary
Sampling Unit variable in the dataset, because the contribution to
variance of any further clustering is incorporated to the PSU
variance. This is based on the 'ultimate cluster method' for variance
calculation.

Does it mean that, when designing a sample, the number of Secondary
Sampling Units is irrelevant for standard errors calculation purposes?
That would mean that if, for example, one selects first municipalities
(PSUs), then census tracts (SSUs) within municipalities and then
individuals within census tracts, it is the same to go for a design
with one census tract with 100 individuals per municipality than to go
for 10 census tracts with 10 individuals each per municipality,
although the second way increases the variability in the sample.

Many thanks in advance,

Angel Rodriguez-Laso
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