Re: st: Logarithmic transformation in psm results

[Maarten buis <maartenbuis@yahoo.co.uk>]

--- On Thu, 17/3/11, Sergio wrote:
> I'm  estimating propensity score matching (with psmatch2
> routine) for a sample of firms participating in a program.
> My outcome variable (turnover of the firm) is expressed
> in logarithm <snip> How can I transform the results in
> order to interpret this results in terms of the original
> values.

You can exponeniate the ATT, but it will represent the 
ratio of geometric means rather than a difference in
arithmatic means. Both geometric and arithmatic means are
valid measures of central tendency, and both a difference
and a ratio are valid ways of comparing groups, so you
could do it that way. However, it is unconventional, so you
need to spent some time/space explaining the results.

This trick, in the linear regression context, is explained
in:
Roger Newson (2003) "Stata tip 1: The eform() option of 
regress". The Stata Journal, 3(4): 445.
<http://www.stata-journal.com/article.html?article=st0054>

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------


      

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