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Article #74Vegetation cluster testing using MRPP
From: Curt Seeliger
Date: Mon, 18 May 1998 00:00
Date: Mon, 18 May 1998 00:00
29 lines
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1875 bytes
Folks, I'm currently at a loss. I'm developing vegetation types using
standard hierarchic clustering techniques (Euclidian distance, Ward's
method). I'm testing these groups using Multiple-Response Permutation
Procedures, which estimates the likelyhood of finding tighter clusters.
MRPP results in p-values ranging from 0.0002 to 0.90 for clusters derived
in this manner, depending on how I transform the data matrix before
clustering.
My problem is that groupings which are statistically significant do not
appear to be of any ecological meaning. I'm fairly boggled by these
results, as I would assume that any sort of clustering method would always
produce groupings which are at least better than random (p < 0.50), but
this does not seem to be the case.
Any help would be appreciated. Thanks.
cur
___________________________________________________________________
DIRT /\ FIRST! | Curt Seeliger
/ \ | Humbled State University
/ \ |
/\____/\ | reply to cws1 at axe dot humboldt dot edu
/--\___\_\ |
/___/ / \ |
/ \__/ _\ |
/_\_____/___/__\ |
Nature laughs last. |
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 10d632,df6da55d2b429032,start X-Google-Attributes: gid10d632,public X-Google-Thread: 115fe3,df6da55d2b429032,start X-Google-Attributes: gid115fe3,public X-Google-Thread: feea0,df6da55d2b429032,start X-Google-Attributes: gidfeea0,public From: Curt Seeliger <cws1@dirt.first!> Subject: Vegetation cluster testing using MRPP Date: 1998/05/18 Message-ID: <Pine.OSF.3.96.980518070912.21248B-100000@axe.humboldt.edu> X-Deja-AN: 354321821 Mime-Version: 1.0 X-Sender: cws1@axe.humboldt.edu Content-Type: TEXT/PLAIN; charset=US-ASCII Organization: CSUnet Newsgroups: sci.stat.math,sci.bio.ecology,bionet.plants