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st: Stata 12: does new xtmixed make -pwigls- obsolete?


From   Carter Rees <carterrees@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: Stata 12: does new xtmixed make -pwigls- obsolete?
Date   Thu, 11 Aug 2011 13:56:29 -0700

Hi Statlisters,


Stata 12 now allows the use of both level 1 and level 2 weights in
multilevel models.  I am wondering what this means for the -pwigls-
command.

A bit of preliminary analysis reveals the following.

************************.
use http://www.stata-press.com/data/r12/pisa2000, clear

xtmixed isei female high_school college one_for both_for test_lang
[pw=w_fstuwt] || id_school:, pweight(wnrschbw) pwscale(size)


*** Level 1 weights using scaling method 2 Pfeffermann et al (1998)
Journal of the Royal Statistical Society B 60, 23-56.

egen sumw = sum(w_fstuwt), by(id_school)

egen nj = count(female), by(id_school)
gen pwt1s2 =  w_fstuwt *nj / sumw

xtmixed isei female high_school college one_for both_for test_lang
[pw=pwt1s2] || id_school:, pweight(wnrschbw)

*********************************************************************.

The output produced by the first -xtmixed- model comes from page 345 of
"STATA
LONGITUDINAL DATA/PANEL DATA REFERENCE MANUAL RELEASE 12" and is the same
as using -pwigls- level 1 weight adjustment method 2 as suggested by
Pfeffermann et al (1998).

I am wondering if the newest version of -xtmixed­ makes -pwigls­ obsolete.
Also, I am looking to trade emails with anyone who has experience using
-gllamm­ in conjunction with ­pwigls- when modeling the Add Health
data.

Cheers,

Carter

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Carter Rees, Ph.D.
Assistant Professor
Arizona State University
School of Criminology and Criminal Justice
602-496-0495
carter.rees@asu.edu





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