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Re: st: IIA violations and subsequent steps


From   "Xiaoheng Zhang" <zhangx@tcd.ie>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: IIA violations and subsequent steps
Date   Mon, 6 Aug 2007 10:27:10 +0100

hello Douglas,

I think IIA is irrelavent to the multinomial logistic regression
because it implies that there is no correlation in terms of latent
utility between any two alternatives.Just wondering why you think in
your case it is violated.Thanks.

Kevin

On 05/08/07, Douglas Garrett <d.garrett@utoronto.ca> wrote:
> Hello!
>   I am currently running a multinomial logistic regression model and
> have found that it violates the IIA assumption.  Of course, one option
> in this case is to fit a nested logit model to these data to allow
> error terms to correlate within parent-levels of the nested structure.
>  However, all of my predictors describe characteristics of
> participants rather than of choices.  To my understanding, this
> person-level type of predictor is not appropriate for a nested logit
> model, as predictors are required typically that vary along with the
> choices themselves.  If that is correct then, how does one handle IIA
> violations in a multinomial logistic model with predictors that are
> choice-invariant?  Might there be a work-around to allow error terms
> of certain choices to correlate prior to running a multinomial model
> such as this?
>
> Many thanks in advance.
>
>
>
> Douglas Garrett
> Grady Lab
> Rotman Research Institute
> Baycrest
> Department of Psychology
> University of Toronto
>
>
>
>
>
>
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-- 
Greetings,

Xiaoheng Zhang (Kevin)
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