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st: Using Sampling weights (pweights) in regression analysis


From   Fatih Yilmaz <fyilmaz@ucalgary.ca>
To   statalist@hsphsun2.harvard.edu
Subject   st: Using Sampling weights (pweights) in regression analysis
Date   Thu, 12 Jul 2012 07:21:04 -0600

Dear Statalist, 

I am having trouble with using sampling weights in my simple regression analysis.

Here is the story: 

The survey data I have is not representative, where some groups were deliberately over or under-sampled. 
    The weights I was provided ara computed as follows:

For group one (strata), population weight is 60%
         				  sample weight is 40% 
					Final Pweight = 60%/40%=1.5 

My questions: 

1- I needed to drop some of the observations from the survey data: outliers, missings obs and also unrelated data.
    so, can I still use the old (initial) weights or do I have to re-weight the data with respect to the dropped observations? 
    Or how problematic could it be to use old weights?

2- Since, my weights were computed as w=(pop%)/(sample%) (in general, some other researchers may compute them as w=(sample%)/(pop%) ), 
when I estimate weighted OLS should I use "reg y x [pw=1/w]" or  ""reg y x [pw=w]".

Could you pls also recommend some resources on sampling weights and regression analysis (preferably practical sources ),

Thanks very much 

Fatih Yilmaz 
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