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st: Linear regression of 'log' predictors


From   Ashwin Ananthakrishnan <ashwinna@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Linear regression of 'log' predictors
Date   Wed, 27 Sep 2006 06:32:09 -0700 (PDT)

Hi,

I have a model where the outcome is length of stay
(los). This variable has some right skew and is not
perfectly 'normal'. 

Is it valid for me to run linear regression of other
predictors on length of stay if the los is not
normally distributed?

If it is not valid, then log (los) is a normally
distributed variable. But how do I interpret the
coefficients of the log(los). I find that
exponentiating log(los) coefficient doesn't seem to be
appropriate as it doesn't yield valid results. For
example p>0.05, but the 95% CI don't overlap 'zero'
which is what I would expect in linear regression.
Also exp(log(los)) doesn't give a similar estimate as
the coefficients if I run the regression on los
directly.

I apologize in advance if my question is either to
basic or difficult to understand.
Thank you.


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