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Re: st: Complex survey with only sampling weights
The study description suggests that this is a complex probability
sample, but by failing to provide you with identifiers for the strata,
PSUs, and secondary sampling units, the original researchers made it
impossible for you to estimate the effects of stratification and
clustering. This is a problem, whether the sample was a true probability
sample or not; your standard errors will almost certainly be too small
regardless of how you calculate them.
The "sampling weights" appear to be poststratification weights based on
external (census or other) estimates of true population values, rather
than design-based probability weights. You can treat them as either
pweights in "regular" Stata commands or as poststratification weights in
-svy- commands and I think you will get the same answers either way,
although if you use them as poststratification weights, you have to be
more careful about subsetting.
In any event, Ana is right; the failure of the researchers to give you
enough information about the design and the weights is not a rationale
for ignoring the weights, especially for simple tabulations.
Michael
Ana Gabriela Guerrero Serdan wrote:
the survey you describe is complex but it doesnt mean that is not random. Its just that to save costs or to be sure that they do include specific groups/workers they have done stratification and clustering.
You probably need to use svy commands in Stata. But his depends on what you are intersting on estimating, for population totals and descriptives you certainly would need.
SPSS version 12 has a complex samples options, so you would be able to get this also in SPSS.
see svy commands in Stata
take a look at Cameron and Trivedi, microeconometricts,chapter on stratified and cluster samples.
rgds,
Gaby
--- On Fri, 5/29/09, [ISO-8859-1] Fernando Terrés <[email protected]> wrote:
From: [ISO-8859-1] Fernando Terrés <[email protected]>
Subject: st: Complex survey with only sampling weights
To: [email protected]
Date: Friday, May 29, 2009, 5:50 AM
I need to analyze an official survey,
with data on 11,054 workers, were
the sampling design is according to the survey company:
'multistage,
stratified by clusters, with random selection of both PSU
(602
undisclosed municipalities), and secondary sampling units
(undisclosed
census sections), and the last sample units (workers) are
selected by
random routes and quotes'. They provide sampling weights
that are (1681)
unique values for each combination of gender (2), region
(17), firm size
(6), and economic activity (13).
My question is very simple: is this a probabilistic
sampling design? I
suspect that it is not, but I cast some doubts because the
documentation
disclosed by the official bureau that commissioned the
survey clearly
insists on using the weights (they present a word document
tabulating
them), that are the only sampling information included in
the SPSS files
that they provide (this reinforces my doubts, because I'm
using Stata
10, which correctly uses the sampling weights, while to my
knowledge
SPSS only uses frequency weights).
Thank you in advance,
Fernando.
--
Fernando Terres
Lecturer. PhD candidate
CERPIE/Research
Universitat Politecnica de Catalunya
Diagonal, 647 - 10
08028 Barcelona (Spain)
+34.934.010.708
[email protected]
http://cerpie.upc.edu
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--
Michael I. Lichter, Ph.D. <[email protected]>
Research Assistant Professor & NRSA Fellow
UB Department of Family Medicine / Primary Care Research Institute
UB Clinical Center, 462 Grider Street, Buffalo, NY 14215
Office: CC 125 / Phone: 716-898-4751 / FAX: 716-898-3536
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