
From  Ronnie Babigumira <rb.glists@gmail.com> 
To  statalist@hsphsun2.harvard.edu 
Subject  Re: st: RE getting rid of the outliners 
Date  Mon, 01 May 2006 12:31:29 +0200 
Ronnie:
I had the same problem with sending to Vora instead of the
statalist (so Vora received multiple copies my email before I found out what the problem was, sorry about that)
In my not overly humble opinion, determining outliers this way
is nothing more than applying rules of thumb, and it is bad
practice to let your analysis be influenced by a blind application of a single rule of thumb. I am a regression man,
so when I am looking for outliers I look at scatter plots, various plots involving residuals, cook's distances, and leverages. I than try to identify points that worry me and try to find out why they are special. Than I decide what I am going to do about them, and in many cases the answer is nothing.
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/

Original Message
From: ownerstatalist@hsphsun2.harvard.edu [mailto:ownerstatalist@hsphsun2.harvard.edu]On Behalf Of Ronnie Babigumira
Sent: maandag 1 mei 2006 11:24
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: RE getting rid of the outliners
Maarten, I had written in earlier suggesting lv (output below) or iqr (I just checked and for some reason, my
response went to Vora N and not to the list), however, your response is more true to the original posting.
That said, I have a follow up question for you
Using the fences created by
local u = r(p75) + (3/2) * (r(p75)  r(p25))
local l = r(p25)  (3/2) * (r(p75)  r(p25))
Would capture "mild" outliers. So my question is, how does this sit with the discussion in for example Hamilton,
Statistics with Stata, which distinguishes between mild and severe outliers pointing out that it is severe outliers that
create problems for many statistical techniques.
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