Hello, I have some questions on doing group comparisons with thickness,
area and volume. Many thanks in advance for any help!
1) For a DOSS design with group and gender as categorical factors, I see
that an interaction contrast ("Is there a group-gender interaction in the
mean thickness?") still exists - but what does this contrast mean, given
that DOSS by definition doesn't allow for interactions?
2) it makes sense that measures such as thickness are analysed vertex-wise
in QDEC, however what does it mean when the dependent variable is area or
volume - measures that do not make physical sense for a single vertex but
only at the level of a region consisting of *several* vertices?
3) For values extracted from atlas regions with aparcstats2table, it seems
that the product of the extracted CT and area is in the same order of
magnitude as the extracted volume, but never really the same or even close
- why, when the volume of a region should theoretically be the product of
its surface area by its thickness?
Tudor
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