[Limdep Nlogit List] best/worst in NLOGIT6

[Thomas Eagle]

I think you'll find NLOGIT estimates it as I described as the best-worst option...  but Bill Greene can explain it better than me.  That is why I referred you to Louviere, Flynn, and Marley (2015) Best-Worst Scaling: Theory, Methods, and Applications.  They lay out in more detail what Flynn, Louviere, et al wrote in 2008.



Just trying to help...



Tom



-----Original Message-----
From: limdep-bounces at mailman.sydney.edu.au <limdep-bounces at mailman.sydney.edu.au> On Behalf Of Michael Burton
Sent: Monday, January 17, 2022 5:29 PM
To: Limdep and Nlogit Mailing List <limdep at mailman.sydney.edu.au>; limdep at limdep.itls.usyd.edu.au
Subject: Re: [Limdep Nlogit List] best/worst in NLOGIT6



Tom



That's not my problem.

If you estimate the 'stacked' model (Louviere et al p36-37) you are estimating a model that internally inconsistent, by construction.  That's because the gumbel error term isn't symmetric.  Where that's recognised (e.g Flynn et al, 2008, BMC Medical Research Methodology) its not seen as a big enough issue to prevent the approach being used.



Delle Site et al (2019) set out the theory (DOI: 10.1016/j.trb.2019.07.014) and a reading of that paper suggests the Nlogit6 can estimate it correctly (i.e. that the probabilities for the worst choices are defined by a 'reverse' logit).  So the purpose of my question is to check if the best/worst command in Nlogit6 actually does that.



Michael





-----Original Message-----

From: limdep-bounces at mailman.sydney.edu.au<mailto:limdep-bounces at mailman.sydney.edu.au> <limdep-bounces at mailman.sydney.edu.au<mailto:limdep-bounces at mailman.sydney.edu.au>> On Behalf Of Thomas Eagle

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Subject: Re: [Limdep Nlogit List] best/worst in NLOGIT6



There are several ways to do this.  You should look at Louviere's book on Best-Worst modeling to see some examples.  The MaxDiff approach is to generate tasks for the best choice and generate tasks for the worst choice.  You use dummy or effects coding for the items in the tasks.  The best tasks are all coded normally.  The worst tasks have all their dummy or effects coded values multiplied by -1.  If you wish to use the best worst coding then the best alternative is dropped from the generated worst tasks.



Tom Eagle



-----Original Message-----

From: limdep-bounces at mailman.sydney.edu.au<mailto:limdep-bounces at mailman.sydney.edu.au> <limdep-bounces at mailman.sydney.edu.au<mailto:limdep-bounces at mailman.sydney.edu.au>> On Behalf Of Michael Burton

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To: limdep at limdep.itls.usyd.edu.au<mailto:limdep at limdep.itls.usyd.edu.au>

Subject: [Limdep Nlogit List] best/worst in NLOGIT6



I am wondering how the 'worst' choices are dealt with in estimation.  Is the 'reverse' logit applied to the worst choices, so the error term is multiplied by -1 and the best and worst choice specification is strictly consistent, or is the more usual 'stacked' approach taken, where marginal utilities of the 'worst' are flipped, but not the error term?

Thanks

Michael



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