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st: Complex survey design


From   sergio salis <ssalis22@yahoo.it>
To   statalist@hsphsun2.harvard.edu
Subject   st: Complex survey design
Date   Thu, 19 Oct 2006 19:52:19 +0200 (CEST)

Dear all,

I have never used the complex survey design in stata
and I would really appreciate if you could give me an
advice. I have a firm-level dataset which includes 2
subsets. The first subset includes data that I don't
want to analyse, while the second is the one of
interest.
My aim is to draw statistics for each region in the
subset 2.
I suppose that I should proceed as follows:

Create one identifier for each reg in subset 2
 
gen reg1=1 if subsample==2 & region==1
replace reg1=0 if reg1!=1
(do the same for all the regions...)

Now I would calculate the mean as follows:

svy: mean productivity, sub(reg1)
svy: mean productivity, sub(reg2)
....
svy: mean productivity, sub(regN)

I would do so because I realised that the new commands
(stata 9) for svy do not include the option 'by'
previously available. Is the way of proceeding
described above correct to obtain the regional means?
(I guess that first dropping the observations for
which subset==2 and then creating the reg dummies is
completely wrong.)

I read on this webpage
http://www.cpc.unc.edu/services/computer/presentations/statatutorial/example31.html

that using 'if' to analyse subsets of the dataset
(instead of the subpop option) is wrong since for the
variance, standard error, and confidence intervals to
be calculated properly svy must use all the available
observations. Hence the only way to proceed seems to
be as I described above...please let me know whether I
am following the right procedure.
Thanks in advance for your help

Sergio




 
--- Maarten Buis <M.Buis@fsw.vu.nl> ha scritto: 

> Jenny:
> Have a look at the thread started with:
>
http://www.stata.com/statalist/archive/2006-10/msg00196.html
> and continued at
>
http://www.stata.com/statalist/archive/2006-10/msg00198.html
> 
> HTH,
> Maarten
> 
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology 
> Vrije Universiteit Amsterdam 
> Boelelaan 1081 
> 1081 HV Amsterdam 
> The Netherlands
> 
> visiting adress:
> Buitenveldertselaan 3 (Metropolitan), room Z434 
> 
> +31 20 5986715
> 
> http://home.fsw.vu.nl/m.buis/
> -----------------------------------------
> 
> --- Jenny Säve-Söderbergh wrote:
>  
> I have data on individuals either selecting funds
> for their portfolio or not
> selecting funds(1 /0 variable). For those who did
> select funds, I have an
> ordinal variable representing the choice of a high,
> medium or low risk fund
> (risk=1,2,3). I am interested only in the choice of
> portfolio risk, but I want
> to control for the possible selection arising from
> not everyone selecting
> funds. Therefore I want to simultaneously estimate
> an ordinal logit model and a
> Heckman selection model. 
> 
> 
> Would anyone know how I can do this? Would it be
> possible just to do a probit
> equation on the first choice, calculate the Mills
> ratio, and then include these
> in the ordinal probit?
> 
>  
> 
> *
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> *  
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> *   http://www.ats.ucla.edu/stat/stata/
> 


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