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st: RE: prvalue / dummy variables


From   "Maarten Buis" <M.Buis@fsw.vu.nl>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: prvalue / dummy variables
Date   Tue, 4 Jul 2006 11:53:10 +0200

--- Jochen Hirschle wrote:
> My question concerns the use of dummy-variables
> within prvalue. As I only wish to control for 
> certain (dummy)variables (sex, place of birth, 
> etc.) and didn't wanted to produce separate 
> estimations for each value (e.g. sex=0, sex=1), 
> I was using the mean option for the dummy 
> variables just as for metric variables 
> (e.g. age). Does that make sense? How can I 
> interpret the estimated probabilities then? Can 
> I say that these probabilities apply for a group 
> which has an underlying structure concerning sex, 

Jochen:
Say you are calculating the probabilities for 
different values of age but keep the effects of 
other variables at their mean, than you are looking 
at how the probability changes as age changes for 
an otherwise "mean/normal/typical" person. So if 
you keep the variable sex at it's mean you are 
looking at the effect of age for someone who is say 
52% female. Now, some would argue that someone who 
is 52% female is not very typical, but you can also 
see this as averaging the effect of age over males 
and females. I have no problems with the latter 
interpretation but others do. So it is probably easier 
to use for nominal variables like sex and birthplace 
the mode to choose the "typical" individual, i.e. fix 
continuous variables at their mean and nominal 
variables at their mode.

HTH,
Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology 
Vrije Universiteit Amsterdam 
Boelelaan 1081 
1081 HV Amsterdam 
The Netherlands

visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214 

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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