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RE: st: RE: Moderation effect by splitting the sample


From   "David Radwin" <dradwin@mprinc.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Moderation effect by splitting the sample
Date   Fri, 21 Dec 2012 09:02:24 -0800 (PST)

Ebru,

Again, I don't think this is necessarily the best approach for your
situation, but amending Nick's code in
http://www.stata.com/statalist/archive/2012-12/msg00758.html , it would be
something like this:

sysuse auto
su weight, detail
gen byte mysplit = cond(weight >= r(p75), 1, cond(weight <= r(p25), 0, .))


David
--
David Radwin
Senior Research Associate
MPR Associates, Inc.
2150 Shattuck Ave., Suite 800
Berkeley, CA 94704
Phone: 510-849-4942
Fax: 510-849-0794

www.mprinc.com


> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
> statalist@hsphsun2.harvard.edu] On Behalf Of Ebru Ozturk
> Sent: Friday, December 21, 2012 12:45 AM
> To: statalist@hsphsun2.harvard.edu
> Subject: RE: st: RE: Moderation effect by splitting the sample
> 
> David, thank you. Can you also give the Stata commands for comparing
upper
> and lower quartiles?
> 
> Kind regards
> Ebru
> 
> ----------------------------------------
> > From: dradwin@mprinc.com
> > To: statalist@hsphsun2.harvard.edu
> > Subject: st: RE: Moderation effect by splitting the sample
> > Date: Thu, 20 Dec 2012 11:50:45 -0800
> >
> > Ebru,
> >
> > I can't say for sure without knowing more about what you are trying to
> do,
> > but regarding splitting continuous variables, see this post and the
> > references therein:
> >
> > http://www.stata.com/statalist/archive/2011-03/msg00154.html
> >
> > If you do split the variable anyway, consider comparing upper and
lower
> > terciles or quartiles (and not the upper and lower halves as a
previous
> > email intimated) to minimize loss of efficiency:
> >
> > Gelman, A., & Park, D. K. (2009). Splitting a predictor at the upper
> > quarter or third and the lower quarter or third. The American
> > Statistician, 63(1), 1-8.
> > http://www.stat.columbia.edu/~gelman/research/published/thirds5.pdf
> >
> > David
> > --
> > David Radwin
> > Senior Research Associate
> > MPR Associates, Inc.
> > 2150 Shattuck Ave., Suite 800
> > Berkeley, CA 94704
> > Phone: 510-849-4942
> > Fax: 510-849-0794
> >
> > www.mprinc.com
> >
> >
> > > -----Original Message-----
> > > From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
> > > statalist@hsphsun2.harvard.edu] On Behalf Of Ebru Ozturk
> > > Sent: Thursday, December 20, 2012 11:42 AM
> > > To: statalist@hsphsun2.harvard.edu
> > > Subject: st: Moderation effect by splitting the sample
> > >
> > >
> > > Dear All,
> > >
> > > For non-linear models, I want to test the moderation effect of X
> > variable.
> > > Can I test this moderation effect by spliting the sample according
to
> X
> > > variable (moderator)?
> > >
> > > Kind regards
> > > Ebru
> >
> > *
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