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RE: st: Simplification of formula in logistic regression


From   "David Radwin" <dradwin@mprinc.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Simplification of formula in logistic regression
Date   Mon, 16 May 2011 11:43:53 -0700 (PDT)

This is true, and it raises the issue of false precision, which is also to
be avoided. An old joke illustrates the problem:

-------

A visitor to a natural history museum is looking at a fossilized dinosaur
skeleton. A guard nearby tells the visitor, "That dinosaur died 90,000,006
years ago."

"Really?" asks the visitor skeptically. "How did you arrive at that exact
number?"

"It's simple," replies the guard. "It died 90,000,000 years before I
started working here, and that was six years ago."

--------

David
--
David Radwin
Research Associate
MPR Associates, Inc.
2150 Shattuck Ave., Suite 800
Berkeley, CA 94704
Phone: 510-849-4942
Fax: 510-849-0794

www.mprinc.com


> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
> statalist@hsphsun2.harvard.edu] On Behalf Of Marcello Pagano
> Sent: Monday, May 16, 2011 11:22 AM
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: Simplification of formula in logistic regression
> 
> Before knocking this request too much further, one should consider the
> accuracy of the variables going into the equation.  Something like blood
> pressure, which can be measured very accurately at any instant, can vary
> tremendously a minute later.  One should not be fooled by apparent
> accuracy of clinical measures.  The grandaddy (or grandmom??) of all
> these is the Apgar score.  She wanted a measure of the babies at birth
> based on what we would consider very, very loose measures --- e.g.
> Reflex irritability (response of skin simulation to feet) : No response
> (score of 0); Some motion (score of 1); and Cry (score of 2); or Color:
> Blue:Pale (score of 0);  Body Pink: extremities blue (score of 1); and
> completely pink (score of 2) --- and yet the use of this score has
> proven to be a great advance in pediatrics.  An excellent read:
> "The Score" by Atul Gawande
> http://www.newyorker.com/archive/2006/10/09/061009fa_fact
> 
> m.p.

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