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Re: st: svy + aweights


From   Jeph Herrin <stata@spandrel.net>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: svy + aweights
Date   Thu, 10 Nov 2011 14:34:57 -0500

Thanks for the suggestion, but I specifically need to give more
weight to subjects which have more days of observation. For example,
I have

   svy : regress activity female BMI

and would like this regression to give more weight to subjects which
have more days of observation. Using activity/days as the dependent
variable will not do this.

Jeph

On 11/10/2011 1:58 PM, Stas Kolenikov wrote:
Rather than forming the mean activity per day, you might want to
analyze this as a ratio:

svy : ratio activity / day_reported

or whatever would be an appropriate ratio. That way, you will get
correct standard errors without messing with the analytical weights.

On Thu, Nov 10, 2011 at 1:46 PM, Jeph Herrin<stata@spandrel.net>  wrote:

I am analyzing NHANES data (see manual page for -svyset-) using -svy-
commands. My complication is that I am using the subset of subjects for
which there is activity monitoring, and the number of days monitored varies
from 1 to 8. So - to be clear - for some subjects I have 1 day of
monitoring,
and for some I have 2 days, some I have 3, etc. My dependent variable of
interest is daily average activity levels, but I would like this to be
weighted by the number of days monitored. (This is important because there
seems to be a clear relationship between days monitored and age, race, etc).

How do I incorporate this additional level of weighting? For instance,
if I use

  svy : mean depvar [aw=days]

I get an error that weights are not reported.

thanks,
Jeph
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