Yes, an advantage of matching over parametric-only approaches is that you
can include as many variables (or categories of variables) as you like.
it may be difficult to find matches (in which case you'll have to make
some compromises), but if you can you can even include many more variables
than observations. Can't do that with regression obviously.
you can check balance for any of these variables (or any others too).
incidentally, we'll have a new version of our paper ready soon; it has
some new developments in it that might be of interest.
Gary
On Wed, 9 Nov 2005, Christian Fink wrote:
Dear Gary,
can I use a nominal (string) variable with serveral (>>100) different
values (ICD codes for medical diagnoses ) for exact matching? Does this
affect the balance statistics?
Best regards
Christian
Christian Fink
Consultant, M.A. Soziologie
Tel +49 (0)89 978804-14
Fax +49 (0)89 978804-19
Mobil +49 (0)163 328 66 72
christian.fink(a)ramboll-management.com
Rambøll Management GmbH
Joseph-Dollinger-Bogen 26
D-80807 München
www.ramboll-management.de
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-----Original Message-----
From: Gary King [mailto:king@harvard.edu]
Sent: Mittwoch, 28. September 2005 13:53
To: Christian Fink
Subject: RE: MatchIt
just follow the same rules for including variables in regression type
models. So take polychotomous vars and make a set of J-1 dummies out of
its J categories.
Gary
-----Original Message-----
From: "Christian Fink" <CHRF(a)r-m.com>
Date: Wednesday, Sep 28, 2005 3:17 am
Subject: RE: MatchIt
Dear Professor King,
I have one question regarding matching on propensity scores in MatchIt.
Can I use nominal variables when matching on propensity scores? Do they
have to be recoded into binary dummies or can I use non-binary
(polytomous) variables?
Yours sincerely
Christian Fink
Christian Fink Consultant, M.A. SoziologieTel +49
(0)89 978804-14Fax +49 (0)89 978804-19Mobil +49 (0)163 328 66
72christian.fink(a)ramboll-management.com
Rambøll Management GmbHJoseph-Dollinger-Bogen 26D-80807 Münchenwww.ramboll-management.de
__________________________________________________Werte schaffen durch Wissen---
Kopenhagen, Aarhus, Stockholm, Oslo, Hamburg, Berlin, München, Brüssel