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Subject: PCA & CVA questions
Date: Wed, 3 Jun 2009 19:25:10 -0700 (PDT)
From: Kimberly Tice <[email protected]>
To: [email protected]
Hi,
I am new to the morphometrics world, and am having a bit of trouble
figuring out what tests to use to analyze my data and how to interpret
them. I was hoping someone might be able to offer a bit of advice...
I have two types of snails, and I want to determine if they are
different shapes. I've been using the IMP programs, and when I perform
a principal components analysis, I have 1 distinct principal component,
but the two different groups are almost completely overlapping along
that PC. I did a MANOVA of all of the partial warps/uniform warps, but
in this case, I found that the groups were significantly different. How
do I reconcile this with the PCA? Is there any way to determine whether
the differences in the MANOVA are "biologically significant" or exactly
what the shape differences are? Is it appropriate to do an ANOVA on one
principle component?
I also did a CVA, and found 1 significant CV, with an eigenvalue of
0.8. What does the eigenvalue mean? Is there any way to determine how
important this CV is in terms of the amount of variation it explains?
I know these are relatively basic statistics questions, but these tests
are new to me. I'd really appreciate any advice you might have or
information about resources that might be helpful.
Thank you!
Kim
[email protected] <mailto:[email protected]>
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