Re: st: Re: svyset for stratified probability proportional to size design

[Nick Winter <nw53@cornell.edu>]

You only -svyset- one weight variable--which 
correspond to the ultimate probability of 
selection of each observation.  With multiple 
stages of sampling, these weights will be a 
function of the probabilities of selection at 
each stage, possibly with additional corrections 
for non-response, etc.  So the sample might be 
self-weighting at the first stage, but perhaps 
not at lower stages, resulting in non-constant 
weights for the ultimate observations.

So you would do something like:

 . svyset psu1 [pw=weight] , str(strat1) || psu2 , fpc(fpc2) || _n , fpc(fpc3)

Note, however, that if the first stage is 
actually sampled with replacement, than 
lower-level without-replacement sampling is 
ignored.  This will be conservative--your 
reported standard errors will be somewhat larger than they would otherwise be.

--Nick Winter




At 02:37 AM 8/11/2005, you wrote:

> We run on Stata 9, updated all July 5.
>
> We have a complex survey design data set with the first stage stratified
> into two parts.  The primary sampling units (census tracts) have been drawn
> with replacement from each of the two strata with probability proportional
> to population size (PPS) in each of the strata.
>
> We have the total population, the population of each stratum, and the
> population of each PSU.  There are two further stages in the sampling
> design, random sampling of 3 blocks within each PSU without replacement and
> random sampling of 2 households within each block without replacement.
>
> Our difficulty lies in specifying specifying svyset for this design,
> particularly selecting (or not) the pw weights for the first level.  On the
> one hand, we read from texts that the glory of probability proportional to
> population sample is that it doesn't need weights.  On the other hand, we
> see from svyset examples at the UCLA site, that considerable effort has
> gone into calculating the values for the first stage weights with PPS
> design,  though without access to the text, we are unclear how to apply their
> example.
>
> Could any suggest how to at least set up svyset for the first stage of the
> above described design?
>
>  Many thanks,
> Steve Rothenberg
> Instituto Nacional de Salud P�blica
> Cuernavaca, M�xico
>
>
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________________________________________________________
Nicholas J. G. Winter                     607.255.8819 t
Assistant Professor                       607.255.4530 f
Department of Government              nw53@cornell.edu e
Cornell University        falcon.arts.cornell.edu/nw53 w
308 White Hall
Ithaca, NY 14853-4601 


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