
From  Terra Curtis <terra.curtis@cambridgefinance.com> 
To  statalist@hsphsun2.harvard.edu 
Subject  Re: st: RE: areg/xtreg 
Date  Mon, 06 Mar 2006 15:52:56 0500 
Did you add in the constant?
. webuse grunfeld,clear
. qui areg invest kstock mvalue, ab(com)
. qui sum kstock
. local ks = r(mean)
. qui sum mvalu
. local mv = r(mean)
. qui sum invest
. local x1 = (_b[kstock]*`ks' + _b[mvalue]*`mv' + _b[_cons])/r(mean)
. disp "`x1'"
.999999999999999
Scott
Original Message
From: ownerstatalist@hsphsun2.harvard.edu [mailto:owner
statalist@hsphsun2.harvard.edu] On Behalf Of Terra Curtis
Sent: Monday, March 06, 2006 1:35 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: areg/xtreg
I am using Stata 8.2. I have a question regarding what is written in
the Stata manual for areg. The manual reports that "areg identifies
the model by choosing the intercept that makes the prediction calculated
at the means of the independent variables equal to the mean of the
dependent variable: y(hat)=x(hat)*beta"
I have used this fact to try to calculate the "percent of mean
explained" by each independent variable in my regression. For
concreteness, I have regressed like this:
areg depvar indvar1 indvar2 indvar3, absorb(timevar)
For the percent of mean explained calculation, I have taken each
coefficient multiplied by the mean of that independent variable and
divided by the mean of the dependent variable. After I have done this
for all three independent variables, in theory the three percentages
should add up to 1. However, this is not the case. Can anyone see why
not?
Thank you,
Terra Curtis
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