Date:         Sun, 2 Mar 2008 18:29:18 -0600
Reply-To:     Zhicheng Lin <zhichenglin@gmail.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Zhicheng Lin <zhichenglin@gmail.com>
Subject:      outliers detection and exclusion
Content-Type: text/plain; charset=ISO-8859-1

Dear List members,

I have been doing experiments and analyzing data for two years but still
have some basic questions to ask (my field is vision and cognitive
psychology):

1) A general question: When do you exclude outliers and what standards do
you use? I understand that excluding outliers normally won't change much
about Mean but will make SD smaller. But still there are cases we do exclude
outliers not just to make SD look better.

2) A specific one: Suppose we have two conditions A B in the study. When
excluding outliers according to 3SD, do you do this in each condition (i.e.
data in A and B are separated) or on the whole data set (i.e. combination of
A and B)?

Any ideas? Many thanks!

Cheers,

Zhicheng

--
******************************************
Zhicheng Lin
Department of Psychology
University of Minnesota
75 East River Rd, Elliott Hall
Minneapolis, MN 55455


Email: linxx443@umn.edu
Phone: 612-625-2470
Fax: 612-626-2079
http://zhichenglin.googlepages.com/
******************************************

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