Bookmark and Share

Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at

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

st: R: How to "reverse" log transformed result

From   "Carlo Lazzaro" <[email protected]>
To   <[email protected]>
Subject   st: R: How to "reverse" log transformed result
Date   Wed, 28 Sep 2011 14:04:03 +0200

Dear Morten,
I do share the previous comments in that without knowing what you typed is
difficult to advise.
However, for what it worths, back transforming from a log transformation,
the mean on the original scale can be obtained by exp(lm+lv/2), where lm and
lv are the mean and the variance on the log scale, respectively.

See as a useful reference: Briggs, A. and Nixon, R. and Dixon, S. and
Thompson, S. (2005)Parametric modelling of cost data: some simulation
evidence. Health Economics 14(4):pp. 421-428.

Kindest Regards,

-----Messaggio originale-----
Da: [email protected]
[mailto:[email protected]] Per conto di Morten Støver
Inviato: mercoledì 28 settembre 2011 9.41
A: [email protected]
Oggetto: st: How to "reverse" log transformated result

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.
Thank you for your help

*   For searches and help try:

*   For searches and help try:

© Copyright 1996–2018 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   Site index