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Vegetation cluster testing using MRPP

Curt Seeliger cws1 at dirt.first!
Mon May 18 09:22:38 EST 1998


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
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