----- Forwarded message from morphmet_modera...@morphometrics.org -----
Date: Tue, 01 Apr 2014 19:24:59 -0700
From: morphmet_modera...@morphometrics.org
Reply-To: morphmet_modera...@morphometrics.org
Subject: RE: Group differences
To: morphmet@morphometrics.org
----- Forwarded message from "F. James Rohlf" <ro...@life.bio.sunysb.edu> -----
Date: Fri, 21 Mar 2014 19:09:49 -0400
From: "F. James Rohlf" <ro...@life.bio.sunysb.edu>
Reply-To: ro...@life.bio.sunysb.edu
Subject: RE: Group differences
To: morphmet@morphometrics.org
The overall significance test in a CVA and a MANOVA are identical so they must
give the same results for the same data. The purpose of the CVA is just to
perform the extra step of providing an ordination of differences among groups
relative to within-group variation. If you obtain different P-values then
there is some problem such as using a different transformation of the original
Procrustes aligned coordinates. They should both use the coordinates projected
onto the tangent space. Perhaps for one of these analyses you used only a few
PCs from this space?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
F. James Rohlf, Distinguished Professor, Emeritus, 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
> -----Original Message-----
> From: morphmet_modera...@morphometrics.org
> [mailto:morphmet_modera...@morphometrics.org]
> Sent: Friday, March 21, 2014 12:45 PM
> To: morphmet@morphometrics.org
> Subject: Group differences
>
>
> ----- Forwarded message from morphmet_modera...@morphometrics.org -----
>
> Date: Wed, 19 Mar 2014 22:16:24 -0700
> From: morphmet_modera...@morphometrics.org
> Reply-To: morphmet_modera...@morphometrics.org
> Subject: Group differences
> To: morphmet@morphometrics.org
>
> ----- Forwarded message from Patrick Arnold <patrick.arn...@uni-jena.de> -----
>
> Date: Mon, 10 Mar 2014 08:59:14 -0400
> From: Patrick Arnold <patrick.arn...@uni-jena.de>
> Reply-To: Patrick Arnold <patrick.arn...@uni-jena.de>
> Subject: Group differences
> To: morphmet@morphometrics.org
>
> Dear morphometrics,
>
> my data contains 5 a priori determined groups. I did CVA in MorphoJ but I know
> CVA not necessarily reveals significant groups. Thus, I want to verify my
> groups
> statistically. Manova with CVs in Past reveal significant groups, comparison
> between groups in MorphoJ and Past, too. But, if I only use Procrusted
> coordinates or PCs, Manova in Past says there are no significant different
> groups. What do theses results say about my groups. Is significance with CVs
> in
> Manova enough to say that the 5 groups are really different in shape??
>
> Patrick Arnold
>
> Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum
> Friedrich-Schiller-Universität Jena Germany
>
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>
> ----- End forwarded message -----
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