Ada Ma wrote:
> 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.
That would be the calculation I would use if the coefficient was the log
of the odds. But, as I explained in my post, that coefficient _is_ the
odds-ratio, so there's no need to exponentiate it!
Moreover, the 'Celtic' coefficient in the Con vs. Lab model is as I
asserted it to be. Tory candidates are significantly _less_ likely to win
Scottish and Welsh by-elections than Labour ones: saying anything else
flies in the face of the electoral evidence we have (and not just in
by-elections). Notice that the z score on the odds ratio is _negative_:
> -----------------------------------------------------
> | Robust
> bewin | RRR Std. Err. z P>|z|
> -------------+---------------------------------------
> con |
> celtic | 1.96e-17 2.21e-17 -34.21 0.000
and naturally so, since the model - rightly - estimates that by-elections
held in Scotland and Wales reduces the odds of a Tory victory there (at
least over the 1975-2000 period) to be comprehensively less than 1,
relative to Labour. (Remember: even odds = [P=.5].)
So, in effect, I'm still searching for an answer to my first question: why
is this odds-ratio so bizarrely low?
CLIVE NICHOLAS |t: 0(44)191 222 5969
Politics |e: [email protected]
Newcastle University |http://www.ncl.ac.uk/geps
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
