[R] Discretize continous variables....

Johannes Huesing johannes at huesing.name
Sun Jul 20 11:29:57 CEST 2008

Frank E Harrell Jr <f.harrell at vanderbilt.edu> [Sun, Jul 20, 2008 at 12:20:28AM CEST]:
> Johannes Huesing wrote:
>> Because regulatory bodies demand it? 
> And how anyway does this  
> relate to predictors in a model?

Not at all; you're correct. I was mixing the topic of this discussion
up with another kind of silliness.

I had a discussion with a biometrician in a pharmaceutical company
though who stated that when you have only one df to spend it will be
better to dichotomise it at a clinically meaningful point than to
include it as a linear term. He kept the discussion on the ground of
laboratory measurements like sodium, where a deviation from normal
ranges is very significant (and unlike, say, cholesterol, where you
have a gradual interpretation of the value). He has a point there, but
in general the reason for sacrificing information is a mixture of
laziness, the preference for presenting data in tables and to keep the
modelling "consistent" with the tables (for instance to assign an odds
ratio to each cell).
Johannes Hüsing               There is something fascinating about science. 
                              One gets such wholesale returns of conjecture 
mailto:johannes at huesing.name  from such a trifling investment of fact.                
http://derwisch.wikidot.com         (Mark Twain, "Life on the Mississippi")

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