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Re: st: how to access e(b) and e(V)


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: how to access e(b) and e(V)
Date   Tue, 20 Oct 2009 12:24:45 +0000 (GMT)

--- On Tue, 20/10/09, Philomela@gmx.net wrote:
> due to the log transformation i have the following problem:
> exp(E(ln(Consumption))) is not equal to E(Consumption).
> I thought more precise estimates would help-but as it
> turned out now- they don't.

Appart from the two solutions I already gave you can use the
fact this way you get the conditional geometric means rather
than the conditional arithmatic means. All you have to do is
find some reason why in your case geometric means are 
preferable over arithmatic means ;-) In the example below I
illustrate that -regress- with log transformed dependent 
variables can be used to get the geometric means, and -glm-
can be used to ge the arithmatic means.

*------------- begin example -----------
sysuse nlsw88, clear
gen ln_w = ln(wage)

xi: regress ln_w i.race
est store ols

xi: glm wage i.race, link(log)
est store glm

bys race: ameans wage

est restore ols
adjust, by(race) exp

est restore glm
adjust, by(race) exp
*------------ end example ---------------
(For more on examples I sent to the Statalist see:
http://www.maartenbuis.nl/example_faq )

More seriously, this is interesting is a nerdish
sorta way, but practically I would use -glm-.

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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