Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: How to "reverse" log transformated result


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
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 <morten.stover@ntnu.no> 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.

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index