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Re: st:. : [problem with outliers in regression]


From   Nazaria Solferino <[email protected]>
To   [email protected]
Subject   Re: st:. : [problem with outliers in regression]
Date   Wed, 7 Aug 2002 18:36:06 +0200 (CEST)

Thank you for your help.
Could you give me some suggestions about
transformation?


> Hello! I'm a new Stata user and I'm not very good at
> using it yet. I hope some one can help with my
> problem. I've a large dataset, with some outliers,
and
> I'd like to manage variables, that I have, only in a
> restricted range(without dropping observations) I've
> thought I could give a zero value to all veriables
> outside a certain range so I mean I should generate
a
> newvar=oldvar then replace newvar=0 if outside the
> range. First, is this a sattistical correct
procedure?

(Please use informative titles on Statalist messages.)


No. Stata will take the new values of 0 just as
literally 
as the old outlying values. 

One way to exclude outliers is by an -if- condition: 
e.g. 

regress y x1 x2 x3 if y < 10000 

Naturally, there are other approaches to your problem 
including  

1. a robust technique. I've found -qreg- very good. 

2. transformation. 

3. -glm- with a nonlinear link (e.g. log). 



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