 |
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]
Re: st: clustering at 2 levels
For some reason I did not receive Vivian's original post, so I am
responding to Stas's reply.
1. I agree with Stas that meterological stations are not part of the
design. The ordinary procedure is to average the contribution of
nearby stations, not to associate a single station with a village.
2. Vivian's -svyset- is incorrect. It should start by specifying the
Primary Sampling Unit (PSU):
svyset vilid
I would guess that Stata issued the error message because Vivian has
repeated person ID's within village. Vivan doesn't give details
about strata, weights, or subsequent stages of sampling, so I am not
sure what follows. It sounds like Vivan intends to model some
outcome. In that case she should omit the finite population
corrections.
-Steve
On Apr 24, 2008, at 4:32 PM, Stas Kolenikov wrote:
On Wed, Apr 23, 2008 at 3:54 PM, Vivian Hoffmann <[email protected]>
wrote:
Is there an easy way to introduce clustering at multiple levels
when using
ivreg and ivtobit?
I doubt those commands would respond to any -svy- settings. Check with
-svyivreg- though. At any rate,...
My two levels of clusters are village (vilid) and meteorological
station
(id). Villages are randomly sampled from the population of
villages. There
are 21 meteorological stations and I have matched one of these to
each
village by minimum distance.
... as you properly note below, you did not sample your stations, so
they do not belong to the design in any least way. All there is in
your design is clustering on villages (unless you had some
stratification there, and you should know better whether you had
different probabilities of selection leading to sampling weights). You
can model your met stations as fixed effects with dummy variables, or
you can post-stratify on them, although that is somewhat dubious a
solution. Why do you want to do anything with those stations, anyway?
I tried to do 2-stage clustering using svyset <svyset id|| vilid>
but got
the error "Note: stage 1 is sampled with replacement, all further
stages
will be ignored".
I checked the Stata FAQ and apparently the solution to this
problem is to
include a finite population correction for the highest level. But
an FPC
on the met stations doesn't make sense, since these are not
sampled. In
fact these are really more like strata (they cover mutually
exclusive
territory). However these are not true strata and I think it
would be
wrong to treat them as such.
--
Stas Kolenikov, also found at http://stas.kolenikov.name
Small print: Please do not reply to my Gmail address as I don't check
it regularly.
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/