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st: Lowess smoothing with a twist


From   SamL <saml@demog.berkeley.edu>
To   Stata Listserve <statalist@hsphsun2.harvard.edu>
Subject   st: Lowess smoothing with a twist
Date   Tue, 27 Aug 2002 13:04:21 -0700 (PDT)

Is it possible to do a lowess smoothing of some data when the Ns vary
across the dimension of smoothing.  In short, I have data that are
percentages of people who believe in God, for almost every year from
1970-2000.  Unfortunately, the sample sizes vary appreciably by year,
meaning that the percentages are obviously less precisely estimated in
years with fewer cases than in years with lots of cases (fewer can be as
low as 10, and lots can be as high as 150 in this context). I know that
LOWESS smoothing (and other techniques) use nearby years to smooth the
data.  I want to know how I can do that AND also account for the differing
precision (or, what is the same thing, the varying Ns) across time.  Does
anyone know whether and how I might do that in Stata or, barring that,
some other graphing program.

Thanks a bunch.
Sam

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