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st: RE: correlated data


From   David Airey <david.airey@Vanderbilt.Edu>
To   Statalist <statalist@hsphsun2.harvard.edu>
Subject   st: RE: correlated data
Date   Tue, 1 Sep 2009 10:46:41 -0500

.

I thought the point of methods comparison studies was to measure the same units with different methods?

There is a good book on methods comparisons called "Statistical evaluation of measurement errors: Design and analysis of reliability studies" by Graham Dunn.

Nick Cox (and others) also have some methods comparisons ados available at SSC that you could try out (findit bland-altman), but maybe the 3D aspect is throwing you?

You might also look into the "geometric morphometric" literature, particularly the 3D morphometrics literature.

-Dave

Nikolaos Pandis

We have a set of 3-D images constructed from cat scans, and we are
measuring volumes defined by certain anatomical points on the 3-D
images.

The reconstruction/measuring technique is performed using 3 new types of
software and their results will be compared with the results of
validated/reference technique.

The same reconstructions/cat scans are used for all techniques.

The objective is to see how close (do they differ significantly?) the
volume values recorded by each technique are to the values recorded by
the reference technique.

I was thinking along the lines of regression with the volume (continuous)
variable as the dependent variable and technique as the categorical
dependent variable with 4 levels. The reference level would be the the
standard/validated method.

However, how would I account for the fact that the data is correlated
since all measurements for the 4 methods are taken from the same
reconstructions/scans?
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