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# Re: st: Questions on -mlogit-

 From Ada Ma To statalist@hsphsun2.harvard.edu Subject Re: st: Questions on -mlogit- Date Sat, 27 Mar 2004 17:34:55 +0000

Hi Clive,

If your base category is Labour (i.e. Labour=0) then the Conservatives are MORE likely to win if celtic==1, and to calculate the the probability of con==1 given that celtic==1 (and ignoring everything else), the function you should use is:

exp(1.96e-17)/(1+exp(1.96e-17))

Not 1/1.96e-17 as you have used. I don't know anything about the rest of your post.

Ada Ma

Clive Nicholas wrote:

```All,

Just a couple of questions after (re-)running some -mlogit- models.

First, after running one such model (modelling party victories at British
by-elections), one of the coefficients returned looked a bit odd:

-----------------------------------------------------
|               Robust
bewin |        RRR   Std. Err.      z    P>|z|
-------------+---------------------------------------
con          |
celtic |   1.96e-17   2.21e-17   -34.21   0.000

The base category against the Conservatives here is Labour. What this is
saying, if I'm interpreting this (quasi-)odds ratio correctly, is that,
after I

. display 1/0.0000000000000000196
5.102e+16

the model is saying that the odds of Labour winning a by-election in
either Scotland or Wales are 51,020,000,000,000,000 times greater than the
Conservatives, Now, I'd certainly expect Labour's odds to be higher in
this region simply because they have been the strongest party there for
many decades, but not quite _this_ high! What to do about this? This model
was estimated along with seven other factors. No more factors could be
added without getting back an -mlogit- model returned with blanks all over
the place.

Second, Dow and Endersby (2004: 117) have recently reported MNL (and MNP)
models together with log_10 hessian condition numbers, which I think would
be useful to report, for the reasons they mention. -search-ing and
-findit- only produced the -hessian- option in -ml-, which isn't what I'm
looking for. Is there a way of reporting these after -mlogit- in Stata
8.2?

Ta.

CLIVE NICHOLAS        |t: 0(44)191 222 5969
Politics Building     |e: clive.nicholas@ncl.ac.uk
School of Geography,  |f: 0(44)870 126 2421
Politics & Sociology |
University of         |
Newcastle-upon-Tyne  |
Newcastle-upon-Tyne   |
NE1 7RU		      |
United Kingdom	      |http://www.ncl.ac.uk/geps

Dow JA and Endersby JW (2004) "Multinomial probit and multinomial logit: a
comparison of choice models for voting research", ELECTORAL STUDIES 23(1):
107-22.
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```
```--
Ada Ma
Research Assistant
Department of Economics
University of Aberdeen
Edward Wright Building F55
http://www.abdn.ac.uk/economics/
http://www.abdn.ac.uk/~pec187/firstpage.htm
Tel:   +44 1224 273417
Fax:   +44 1224 272181
Email: a.ma@abdn.ac.uk

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```

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