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st: Using stratified samples in STATA / giving weights


From   Thomas Klausch <thomas.klausch@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Using stratified samples in STATA / giving weights
Date   Sat, 5 Sep 2009 17:31:21 +0200

Dear list members,

I am planning to survey a stratified sample from a relatively small
finite population of which I know the size. I am not too familiar with
weighting techniques and the STATA -svy- command family, which is why
I write. Maybe somebody can give useful advice.

My popluation consists of size n=7800, with n=700 and n=7100 sized
relevant stratas.

My first question is, how I would decide about a good sample size for
each Strata if I cannot sample more than n=1200. I am particularly
interested in estimates from the smaller strata. So I decided
heuristically to sample n=500 from the small and n=700 from the large
STRATA, but I am not sure if this is reasonable to do.

My knowledge about weighting tells me that this gives rise to weights
of approx. .22 for the small strata and approx. 1.56 for the large
strata. In SPSS I would know how to use the weights function, as there
is only one. STATA provides several weight options -fweight-,
-pweight-, -aweight- and -iweight-. I have tested in STATA that it
gives the same estimates using -iweight- than SPSS does using the
WEIGHT BY command.

My second question is if -iweight- is reasonable to use for my case
when estimating regression models (in particular logistic panel
models).
My third question is whether there is a, maybe better, way to use the
options provided in the -svy- command family to specify the survey
design. Maybe there is also a third way I do not know of.

If anybody could give advice on these questions or further reference
for detailed information on -svy- I'd appreciate it a lot.

Many thanks

Thomas
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