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Re:st: How to weight datasets?


From   "rafaelcla" <rafaelcla@uol.com.br>
To   "statalist" <statalist@hsphsun2.harvard.edu>
Subject   Re:st: How to weight datasets?
Date   Sat, 30 Aug 2008 21:46:37 -0300

Hagen,

In order to obtain weighted estimations – and consequently fit your data on a specific population – you’ll need to “place the weight” on estimation command NOT on the data. “To Weight” the data (like, by replicate a single case X times according to its weight) does not work in many, many situations…and will possibly drive you to wrong results…so, don’t do this unless you are totally sure about it.

As I’m not exactly sure about the sample design (and the kind of weight) you have…I’ll give you an example as if you were using “probability weights”. After loading your dataset, to obtain a weighted mean of variable “X”, using the weight variable “Y” (that should indicate the probability weight or just PW), all you need to do is type:

mean X [pw=Y] 

In fact, as you can note, the “weighting procedure” (described by the extension “[pw=Y]” on the command above) works as an extension of the command…not a command itself (if you type just "mean X"stata will give you the unweighted mean). 

Not all kinds of weight (PW, AW, IW…) work with all commands…but you can figure this out on the help file of the commands you want to proceed with. 

Best,
Rafael Claro




---------- Início da mensagem original -----------

      De: owner-statalist@hsphsun2.harvard.edu
    Para: statalist@hsphsun2.harvard.edu
      Cc: 
    Data: Sat, 30 Aug 2008 15:24:35 +0200
 Assunto: st: How to weight datasets?

> I have four separate datasets that I would like to weight in order to fit them on a specific population. I know that Stata has commands like pweight or aweight, but how exactly do I use them to create a weighted dataset?
> Maybe someone has a do-file to show me or simply write me the needed commands. The Stata- help is no good for me, since I`m not able to use it correctly. 
> 
> HELP
> 
> Thanks a lot
> 
> 
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