hi all - in theory this data compression issue is a problem, but in
practice
I think that it's not really to be worried about if you are averaging
over
voxels. I think the main worry would come about in computing variance
measures over data extracted directly from Y.mad from a single voxel. If
others on the list think this is wrong please let me know.
with the size of ROIs that we usually use (10-30 voxels) any quantization
noise should be averaged out, and that noise should only impinge on your
signal if you are working with very tiny effect. In practice we have
never found this
to be the case.
cheers
russ
----
Russell A. Poldrack, Ph.D.
UCLA Department of Psychology
Franz Hall, Box 951563
Los Angeles, CA 90095-1563
email: [log in to unmask]
phone: 310-794-1224
fax: 310-206-5895
web: http://www.poldracklab.org/
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