Re: st: ROC with complex data sets

[Steven Joel Hirsch Samuels <sjhsamuels@earthlink.net>]

Sharonda,

I believe you are mistaken.

Although the weighting computations may be complicated, all  
probability surveys wind up with a "final" weight variable; call it  
"final_wt".  It is the one that would be designated the probability  
weight in -svyset- , via "[pweight=final_wt]", and it is the one you  
would round to create a frequency weight.  If that final weight  
variable is not present in your data, then contact the survey  
developers or the documentation for advice on how to calculate it.

Stratification and clustering will not affect the computation of  
sensitivity and specificity and, by extension, the ROC curves.  Only  
the p-values, standard errors, and C.I.'s will be incorrect.

Note: There can be many "final weights" in a survey data set. but  
only one will be used at a time.  In the 1999-2000 National Health  
And Nutrition Examination Survey, for example, there were exam  
weights, interview Weights, and a variety of weights for analyses of  
chemicals that were measured only in sub-samples. Problems do arise  
for investigators who want to analyse the association of two  
chemicals  not always measured together.

Steven

On Aug 21, 2007, at 10:48 AM, Taylor, Sharonda A. wrote:


> Steven,
> Thanks for the input. The problem is that I cannot simply convert  
> pweights to frequency weights  by rounding. They are derived at in  
> very different ways. Even with using svyset, I cannot run ROC  
> because it does not take into account the complex design or the  
> pweights. Any other suggestions? Am I doomed to hand calculate this?
>
> On Aug 20, 2007, at 8:34 AM, Taylor, Sharonda A. wrote:
>
> > I am very new to research. I am attempting to do ROC analysis using
> > a complex survey that uses pweights. Stata 9.2 uses frequency
> > weights. I understand that pweights and fweights are not
> > interchangeable. Are there any downloads that will allow me to run
> > the analysis with the pweights? Please advise.
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