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st: weights in multivariate analysis


From   "Koeppen, Katja" <Koeppen@demogr.mpg.de>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   st: weights in multivariate analysis
Date   Tue, 30 Mar 2004 11:34:16 +0200

Dear all,

I have a question concerning the use of weights in multivariate analysis.
Because of the oversampling of a particular subgroup in my data set, I had
to use a given weighting factor. I estimated a multiplicative
intensity-regression model. I know that I cannot say anything about my
t-statistic now, because the weighted number of cases is different than the
unweighted number of cases. Tests of significance are not valid anymore
because the standard errors are biased. I know that there are procedures in
SAS and SPSS to normalize the weights. I don't know about any function inn
STATA that would allow to adjust the weights. That's why I adjusted the
weighting factor by dividing the weight variable by the mean of the weight
variable. The relative values of the weights do not change but they are
adjusted so that the mean weight in the sample is 1, and the sum of weights
equals the number of cases. Now, I think, the p-values can be used for
interpretation because they are no longer biased. Is this procedure correct?
Or is there any other method how to adjust weights in STATA? And does
anybody know about some literature concerning this topic?

Thank you in advance,

Katja


--------------------------------------------------------
> Katja Köppen
> Max Planck Institute for Demographic Research
> Konrad-Zuse-Str. 1
> 18057 Rostock
> Germany
> tel: +49-381-2081-181
> koeppen@demogr.mpg.de
> 


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