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Re: st: ROC with complex data sets
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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