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Re: re:Re: st: RE: update - trouble with computing marginal effects after a Logit or an Ordered Logit model - Please HELP


From   "Justina Fischer" <JAVFischer@gmx.de>
To   statalist@hsphsun2.harvard.edu
Subject   Re: re:Re: st: RE: update - trouble with computing marginal effects after a Logit or an Ordered Logit model - Please HELP
Date   Thu, 26 Jul 2012 23:15:46 +0200

Hi Jeremy

as non-specialist, I recall somewhat that it may cause some inefficiency in estimation and thus an identification problem.

Best

Justina


-------- Original-Nachricht --------
> Datum: Thu, 26 Jul 2012 23:12:05 +0200
> Von: Jeremy Franklin <jfrankli@ulb.ac.be>
> An: statalist@hsphsun2.harvard.edu
> Betreff: re:Re: st: RE: update - trouble with computing marginal effects after a Logit or an Ordered Logit model - Please HELP

> Hi Justina and thank you for considering my problem;
> 
> This model is one of the 3 i will use in my master degree thesis, in the
> two robustness test model, i do use continuous variables for income for
> example.
> 
> Could you please shed light for me on why having only binary variables as
> independents is not a good idea ? 
> 
> Kind regards;
> 
> Jeremy
> 
> 
> 
> >Hi Jeremy,
> >
> >having only binary variables as independents is not a good idea in
> non-linear models.
> >
> >I suggest that you model age as continuous variable, maybe in a quadratic
> or cubic form.
> >
> >Best
> >
> >Justina
> >-------- Original-Nachricht --------
> >> Datum: Thu, 26 Jul 2012 13:56:21 -0700
> >> Von: "William Buchanan" <william@williambuchanan.net>
> >> An: statalist@hsphsun2.harvard.edu
> >> Betreff: st: RE: update - trouble with computing marginal effects after
> a Logit or an Ordered Logit model - Please HELP
> >
> >> Hi Jeremy,
> >> 
> >> Since you're using Stata 11, I would first suggest reading [U]11.4.3
> >> Factor
> >> Variables.  You can simplify your syntax quite a bit just by looking
> there
> >> and learning how to use factor variables. Then your syntax might look
> >> like:
> >> 
> >> logit mfirstchoice i.mstudy mhomme mchiefwageearner i.mage i.mintpol
> >> i.mpol
> >> i.mincome i.s003##i.s002, vce(cluster s003)
> >> 
> >> One of the issues that I think you're having might be the result of
> >> multicollinearity, since it seems like you're including all of the
> >> possible
> >> categories of some factors in the model.  Using factor variable
> notation
> >> can
> >> help you to reduce that happening quite a bit, since Stata will
> >> automatically exclude a reference group.  
> >> 
> >> Once you fit your model (like the one above), then you can use the
> >> -margins-
> >> command which is part of official Stata (see [R] margins for details
> about
> >> the syntax or type -help margins-).  There are multiple options
> available
> >> and the command is very flexible.  Also, you should include the results
> >> that
> >> you're getting from Stata.  This article from one of the StataJournal
> >> Associate Editors
> >> (http://www.maartenbuis.nl/publications/interactions.pdf)
> >> might be helpful to look at.
> >> 
> >> HTH,
> >> Billy
> >> 
> >> -----Original Message-----
> >> From: owner-statalist@hsphsun2.harvard.edu
> >> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Jeremy
> Franklin
> >> Sent: Thursday, July 26, 2012 1:33 PM
> >> To: statalist@hsphsun2.harvard.edu
> >> Subject: st: update - trouble with computing marginal effects after a
> >> Logit
> >> or an Ordered Logit model - Please HELP
> >> 
> >> Dear all, 
> >> 
> >> Here is my little trouble regarding assessing marginal effects after
> >> running
> >> a logit model on STATA 11: 
> >> 
> >> First, please not that I am a beginner with STATA and what follows
> might
> >> sound ridiculous 
> >> 
> >> For my master degree thesis I decided to test for the role of education
> >> level in assessing the importance of fighting inflation. 
> >> 
> >> Here is my final regression formula: 
> >> 
> >> xi: logit mfirstchoice mstudymid mstudyhigh mhomme mchiefwageearner
> >> mage28_37 mage38_47 mage48_57 mage58 mintpollow mintpolmid
> mintpolhigher
> >> mpolleft mpolright mincomemid mincomehigh i.s003 i.s002 i.s003*i.s002,
> >> vce(cluster s003) 
> >> 
> >> Note that:
> >> - all these variables are binaries
> >> - i.s003 controls for the country effects
> >> - i.s002 controls for the wave (time) effects
> >> - i.s003*i.s002 controls for the country-wave effects
> >> - vce(cluster s003) characterizes the error term 
> >> 
> >> I have the results but my thesis coordinator told me that the
> coefficients
> >> of logit regressions cannot be interpreted like coefficients of a
> linear
> >> regression. Therefore, he suggested me to check for the marginal
> effects
> >> at
> >> the median. The purpose of this last procedure (if I remember well) is
> to
> >> see the marginal effects of one individual having a higher level of
> >> education relative to lower or middle education level.
> >> 
> >> I googled everything, I read the mfx and the margins search page on
> stata
> >> about hundred times, I tried hundreds of formulas, both with mfx and
> >> margins
> >> but i still cannot find the correct one in order to interpret my
> results. 
> >> 
> >> Can ANYONE help me please? It is very important
> >> 
> >> ps: a robustness test included in my thesis uses the following formula
> >> (this
> >> time with ologit as far as the dependent variable takes multiple
> ordered
> >> outcomes): 
> >> 
> >> xi: ologit minflation mstudymid mstudyhigh mhomme mchiefwageearner
> >> mage28_37
> >> mage38_47 mage48_57 mage58 mintpollow mintpolmid mintpolhigher mpolleft
> >> mpolright x047 i.s003 i.s002 i.s003*i.s002, vce(cluster s003)
> >> 
> >> So if it is easier to check for the marginal effects with a ordered
> logit
> >> please let me know.
> >> 
> >> Kind regards;
> >> 
> >> Franklin Jeremy
> >> 
> >> *
> >> *   For searches and help try:
> >> *   http://www.stata.com/help.cgi?search
> >> *   http://www.stata.com/support/statalist/faq
> >> *   http://www.ats.ucla.edu/stat/stata/
> >> 
> >> *
> >> *   For searches and help try:
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> >> *   http://www.stata.com/support/statalist/faq
> >> *   http://www.ats.ucla.edu/stat/stata/
> >
> >-- 
> >Justina AV Fischer, PhD
> >COFIT Fellow
> >World Trade Institute
> >University of Bern
> >
> >homepage: http://www.justinaavfischer.de/
> >e-mail: javfischer@gmx.de. justina.fischer@wti.org
> >papers: http://ideas.repec.org/e/pfi55.html
> >
> >
> >*
> >*   For searches and help try:
> >*   http://www.stata.com/help.cgi?search
> >*   http://www.stata.com/support/statalist/faq
> >*   http://www.ats.ucla.edu/stat/stata/
> >
> >
> 
> 
> *
> *   For searches and help try:
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> *   http://www.ats.ucla.edu/stat/stata/

-- 
Justina AV Fischer, PhD
COFIT Fellow
World Trade Institute
University of Bern

homepage: http://www.justinaavfischer.de/
e-mail: javfischer@gmx.de. justina.fischer@wti.org
papers: http://ideas.repec.org/e/pfi55.html


*
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