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


From   Jeremy Franklin <jfrankli@ulb.ac.be>
To   statalist@hsphsun2.harvard.edu
Subject   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 23:12:05 +0200

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
>> 
>> *
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>
>-- 
>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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>
>


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