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Re: st: How to "reverse" log transformated result
From
Nick Cox <[email protected]>
To
[email protected]
Subject
Re: st: How to "reverse" log transformated result
Date
Wed, 28 Sep 2011 08:53:50 +0100
This sounds like the kind of application in which modelling is better
done with a logarithmic link function.
See for example
http://blog.stata.com/2011/08/22/use-poisson-rather-than-regress-tell-a-friend/
or several similar threads on Statalist recommending -poisson- or
-glm, link(log)-.
Nick
On Wed, Sep 28, 2011 at 8:40 AM, Morten Støver <[email protected]> wrote:
> I'm doing an multilevel linear regression analysis where I try to
> investigate if there are variation in the lenght of the rehabilitation
> process before people are being granted a disability pension. I measure this
> in days, and since my data are very skewed, I've done a log transformation.
> Now I wonder how I can transform the results back to the original scale of
> measurement. As an example, this are the results for the different types of
> diagnosis.
> "Other" diagnosis: (ref)
> Mental disorders: 0.1993938
> Musulosceletal: 0.0840664
>
> If I now try to transform the data back using di exp(.1993938) I get the
> result 1.2206626.
> If I try to analyse the data without log transforming them, I find that the
> mental disorders group have 166 days (95% CI: 75.5-265.6) longer
> rehabilitation time before being granted a disability pension than the
> "other" diagnosis group.
> I guess that the di exp is not the right way to transform the results back,
> but I don't know any other way to do it.
> I'm using Stata 11.
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