Re: st: RE: RE: predicted probabilities of interaction term

[Richard Williams <richardwilliams.ndu@gmail.com>]

At 10:49 AM 7/18/2012, Valle, Giuseppina wrote:
> Thank you for your help -- I was unaware that I needed to use the 
> subpop command when looking at the gender differences with the svy 
> command. In terms of the postestimation commands, I have not located 
> any syntax available that will produced predicted probabilities of 
> the interaction terms with a mlogit. I have 4 values for "race" and 
> 3 values for "relig." I assume that using prtab along with specified 
> values of these two variables would not produce the estimates I am 
> looking for, as that is the only command I have used for predicted 
> probabilities.

If you want to get predicted values for individual cases use the 
-predict- command. If, on the other hand, you want to get predicted 
probabilities for certain combinations of values, check out the 
margins command. e.g. do something like

webuse nhanes2f,clear
svy: mlogit health i.sex##i.race age
margins race#sex, predict(outcome(1)) atmeans
margins race#sex, predict(outcome(2)) atmeans
margins race#sex, predict(outcome(3)) atmeans
margins race#sex, predict(outcome(4)) atmeans
margins race#sex, predict(outcome(5)) atmeans

I believe that would more or less clone what -prtab- does, although I 
personally might drop the -atmeans- option.

The margins command is powerful but complicated (and also a little 
tedious with multiple outcome commands like mlogit). The current 
issue of the Stata Journal has an article on it, and there is also a handout at

http://www.nd.edu/~rwilliam/stats/Margins01.pdf


> Pina
>
> Giuseppina Valle, M.S.
> Department of Sociology
> Doctoral Candidate
> Florida State University
> 526 Bellamy Building
> Tallahassee, FL 32306-2240
>
> Email:   gv08d@my.fsu.edu
>
> ________________________________________
> From: owner-statalist@hsphsun2.harvard.edu 
> [owner-statalist@hsphsun2.harvard.edu] on behalf of William Buchanan 
> [william@williambuchanan.net]
> Sent: Tuesday, July 17, 2012 5:11 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: predicted probabilities of interaction term
>
> Hi Giuseppina,
>
> One suggestion that I have would be to use the -subpop()- option of the
> -svy:- prefix.  This is something that surfaces on the Statalist regularly,
> although it may not be an issue in your specific case.  Either way, the help
> file for -svy- includes the following line:
>
> "Warning:  Using if or in restrictions will often not produce correct
> variance estimates for
>       subpopulations.  To compute estimates for subpopulations, use the
> subpop() option."
>
> With regards to your other question, I would look at -help mlogit
> postestimation- to get an idea of what is already available in Stata to
> calculate the predicted probabilities of the outcome after a multinomial
> logit model.
>
> HTH,
> Billy
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Valle, Giuseppina
> Sent: Tuesday, July 17, 2012 1:38 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: predicted probabilities of interaction term
>
> Hello,
> I was wondering how to run predicted probabilities for a multinomial
> regression with an interaction term.
>
> Here is the syntax I am using:
>
> svy: mlogit timing pledge sexed i.race i.relig i.race#i.relig ///
>         wave4age stepfam singlemo singleda other HSdeg somecoll ///
>         colldeg misseduc lowmidinc highmidinc highinc missinc ///
>         midwest south northeast if gender==0,  ///
>         rrr baseoutcome(2) nolog
>
> I would appreciate any suggestions. Thanks!
>
> Giuseppina Valle
>
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-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
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EMAIL:  Richard.A.Williams.5@ND.Edu
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