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st: correlated data


From   Nikolaos Pandis <npandis@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: correlated data
Date   Mon, 31 Aug 2009 20:33:05 -0700 (PDT)

Hi to all.

I would like to ask the following question.

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?

Any suggestions would be greatly appreciated.

Many thanks,

Nick 



      
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