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Re: st: probit- dprobit


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: probit- dprobit
Date   Fri, 11 May 2007 20:37:03 +0100 (BST)

> At 09:55 AM 5/11/2007, Carola Weiss wrote:
> >Iīm using the probit command to figure out the 
> >impact of tenure to work satisfaction (binary 
> >variable: 1= high work satisfaction).
> >I should estimate the marginal effects by using dprobit.
> >Can anybody tell me whatīs he differnece? I 
> >should only interpret  significance and 
> >direction of the effects. Therefore I only need the probit results,
> >donīt I?

--- Richard Williams <Richard.A.Williams.5@ND.edu> wrote: 
> Why do you think you should only interpret 
> significance and direction of effects?  One of my 
> pet peeves is that people do indeed often only 
> look at sign and significance, and the 
> practical/substantive significance remains 
> unclear.  Marginal effects are one way of getting at substantive
> significance.

I totally agree with Richard. Significant is not the same as relevant.
If I am in a bad mood I tell whomever comes in my office for help that
if they get a non-significant result that only means that they haven't
collected enough data, and if they get a significant result that they
collected too much data. Don't get me wrong, significance testing is a
very elegant and smart solution to an impossible problem, but too often
people attach magical properties to p-values. Just looking at some
predicted probabilities, marginal effects, or odds ratios (I am
actually starting to appreciate those, though I admit they are an
acquired taste)  can tell you so much more. And don't forget graphs!!

Hope this helps,
Maarten

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

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

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


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