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Re: st: Re: Problems with survey sub-group analysis using Stata


From   Ashwin Ananthakrishnan <ashwinna@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Re: Problems with survey sub-group analysis using Stata
Date   Sat, 28 Jul 2007 08:15:27 -0700 (PDT)

I was using the if qualifier.

My command line is:

xi: svy: logistic died i.agecat i.sex i.insurance
i.residence i.income i.liverdisease i.pneumonia
i.heartfailure if diag==1 & kidney==1

I'm not able to use the subpop() option in combination
with logistic.

If I try

xi: svy: logistic died i.agecat i.sex i.insurance
i.residence i.income i.liverdisease i.pneumonia
i.heartfailure, subpop(kidney)

I get the error message "option subpop() not allowed
r(198);"


Ashwin




--- Michael Blasnik <michael.blasnik@verizon.net>
wrote:

> ...
> It would be helpful if you showed your command line.
>  Are you using the -if- 
> qualifier to identify the subgroup, or the subpop()
> option?  The -if- qualifier 
> should be avoided with survey data since it will
> often lead to the problem you 
> describe and, for most purposes, does not use the
> survey design information 
> appropriately.
> 
> Michael Blasnik
> 
> 
> ----- Original Message ----- 
> From: "Ashwin Ananthakrishnan" <ashwinna@yahoo.com>
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Saturday, July 28, 2007 10:02 AM
> Subject: st: Problems with survey sub-group analysis
> using Stata
> 
> 
> > Hi,
> >
> > I'm currently using Stata 9.2 to analyze a survey
> > sample - the Nationwide inpatient sample that uses
> > three different weights (pweight = discwt),
> stratum
> > weight (nis_stratum) and psu weight (hospid)
> >
> > However, I'm running into a problem when I try
> > specific subgroup analyses.
> >
> > When I try to run logistic regression of the
> outcome
> > (say, death from pneumonia) on specific subgroups
> (say
> > age group 65-85) or in the presence of a specific
> > complication (say, acute renal failure), I get the
> > odds ratio estimates but no p-value or confidence
> > intervals, and I get this message "Missing
> standard
> > error due to stratum with single sampling unit". 
> I
> > don't get this message for any of the univariate
> > analysis or for some other subgroups (especially
> those
> > with larger numbers, though that isn't necessarily
> the
> > case always).
> >
> > I did look for strata with single PSU using the
> svydes
> > command. It was suggested to me to try to combine
> the
> > different strata with single PSUs in order to
> avoid
> > getting this error. However, for certain specific
> > subanalyses, nearly all the strata in the dataset
> are
> > listed as having a single PSU. I'm not sure that
> if I
> > try to combine almost all strata into one or two,
> then
> > the entire design of the stratified survey will be
> > lost and my estimates will not be accurate.
> >
> > Have others who are using stata for survey
> analysis
> > run into similar problems? Is there any other way
> > around this problem? or is using SUDAAN the only
> > answer?
> >
> > Thanks,
> >
> > Ashwin
> 
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