----- Forwarded message from
morphmet_modera...@morphometrics.org -----
Date: Fri, 30 Nov 2012
14:14:44 -0800
From: morphmet_modera...@morphometrics.org
Reply-To: morphmet_modera...@morphometrics.org
Subject: RE: PCA and
elliptical confidence
To: morphmet@morphometrics.org
----- Forwarded message from "F.
James Rohlf"
Date: Fri, 30 Nov
2012 12:59:49 -0500
From: "F. James Rohlf"
Reply-To: ro...@life.bio.sunysb.edu
Subject: RE: PCA and elliptical confidence
To:
morphmet@morphometrics.org
A confidence region
shows the uncertainty for the estimate of the mean. It does not imply that
individuals from the groups can be distinguished. With very large sample sizes
the confidence regions will be very small but even if they do not overlap the
scatter of individual observations may broadly overlap. Perhaps you should
compute equal-frequency ellipses – their purpose is to show the range of
dispersion of individuals. The different sizes of these will give you
information about differences in sample variances.
----------------------
F. James Rohlf,
John S. Toll Professor, Stony Brook University
The
much revised 4th editions of Biometry and Statistical Tables are now
available:
http://www.whfreeman.com/Catalog/product/biometry-fourthedition-sokal
http://www.whfreeman.com/Catalog/product/statisticaltables-fourthedition-rohlf
P Please consider the
environment before printing this email
From:
morphmet_modera...@morphometrics.org
[mailto:morphmet_modera...@morphometrics.org]
Sent: Friday, November
30, 2012 1:33 AM
To: morphmet@morphometrics.org
Subject: PCA
and elliptical confidence
----- Forwarded message from dan dkin
-----
Date: Thu, 29 Nov 2012 06:19:37 -0500
From: dan dkin
Reply-To: dan dkin
Subject: PCA and elliptical confidence
To: morphmet@morphometrics.org
Hi,
When I run a PCA and applying elliptical confidence I can
distinguish groups. The ellipses I get are in different radiuses and almost do
not overlap. Therefore, except the difference of the groups does the ellipse
shape tell something (e.g., variance in the groups, etc).
Any
explanation, paper or etc will be welcome.
Thank
-----
End forwarded message -----
----- End forwarded message -----
----- End forwarded message
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