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# st: RE: prvalue / dummy variables

 From "Maarten Buis" To 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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