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st: RE: DATA ANALYSIS QUESTION


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: DATA ANALYSIS QUESTION
Date   Sun, 23 Aug 2009 18:16:21 +0100

(Using all caps is often deprecated in email lists: please don't SHOUT
like that.) 

I don't work in this area, but I find it difficult to imagine that there
is not a literature on this. In addition to the problems you mention,
imagery of this kind is spatial, so there will be some error structure
on that account alone which it would be foolish to ignore. 

Nick 
n.j.cox@durham.ac.uk 

Nikolaos Pandis

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?


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