-------- Original Message --------
Subject: RE: Low sample size problem
Date: Sat, 1 Nov 2008 17:32:37 -0700 (PDT)
From: F. James Rohlf <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Organization: Stony Brook University
To: [email protected]
References: <[EMAIL PROTECTED]>
The obvious question is what do you plan to do with the relative warp
scores? If you wish to use MANOVA or CVA to test for differences between
the two means then there is a sample size problem. However, you could
simply compute the Procrustes distance between the two means and then do
a permutation test to see whether this distance is unusually large. That
test does not require a full rank covariance matrix. In many cases this
test does not have as much power as the standard test but it may be
sufficient in your case.
------------------------
F. James Rohlf, Distinguished Professor
Ecology & Evolution, Stony Brook University
www: http://life.bio.sunysb.edu/ee/rohlf
-----Original Message-----
From: morphmet [mailto:[EMAIL PROTECTED]
Sent: Friday, October 31, 2008 3:35 PM
To: morphmet
Subject: Low sample size problem
-------- Original Message --------
Subject: Low sample size problem
Date: Fri, 31 Oct 2008 11:34:02 -0700 (PDT)
From: Fred Sundstrom <[EMAIL PROTECTED]>
To: <[email protected]>
Dear List
I have a problem with low sample sizes and request your advice.
I have used TpsDig2 to take 13 landmarks on fish from five different
groups. However, in one group I only have 8 specimens and in another
only 12 and unfortunately I cannot get more of these samples.
I understand that I should not used all 22 partial warp scores to
analyze this. My idea the is then to use the first 6 or 7 relative
warps, but is this ok? Or is this is even advisable or is there a
better
(alternative) way of dealing with this problem of more landmarks than
specimens?
Any input is much appreciated!
Best fishes,
Fred Sundstrom
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