[R] lm -- significance of x coefficient when I(x^2) is used

Ramon Diaz-Uriarte ramon-diaz at teleline.es
Wed Sep 27 22:19:48 CEST 2000

```On Wed, 27 Sep 2000, gb wrote:
> On Tue, 26 Sep 2000, Bill Venables wrote:
>
> > At 10:12 26/09/00 +0200, Michael Pronath wrote:
> > >
> > > In "Modern Applied Statistics with S-Plus" 3rd ed., footnote on page 153
> > > regarding a model lm(Gas~Insul/(Temp+I(Temp^2))-1,whiteside), I read
> [cut]
> > It comes back to the question of where would someone have good reason a
> > priori to pose the question "Is the curve flat HERE, and this very special
> > temperature?"  If there is no good reason to pose the question, why force
> > the model to conform to this arbitrary restrictrion?  Notice that this is
> > not quite the same thing as variable selection where Occam's principle is
> > the good reason for considering whether or not coefficients are zero.
> [cut]
>
> Where can I find a description of "Occam's principle"? I vaguely recall
> "Occam's razor", which I guess is the same thing?

A discussion and critique of this and other similar parsimony arguments
can be found in E. Sober's "Reconstructing the past.  Parsimony, evolution and
inference" (1998, The MIT Press).  The main theme of the book is phylogenetic
reconstruction, but if I recall correctly the first couple of chapters deal in
general with Ockham's razor, parsimony, etc, and their problems and
justifications.  By the same philosopher of science there is a chapter titled
"Let's razor Ockham's razor" in the book "Explanation and its limits" by D.
Knowles (1990, Cambridge University Press).

Ramon

>
> Thanks,
>
> Göran
> --
>  Göran Broström                      tel: +46 90 786 5223
>  Department of Statistics            fax: +46 90 786 6614
>  Umeå University
>  SE-90187 Umeå, Sweden             e-mail: gb at stat.umu.se
>
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--
Ramón Díaz-Uriarte
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28016 Madrid
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email:ramon-diaz at teleline.es
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