Just a couple of thoughts.
It depends on what you want to control for AND how you want to control for it. For example, if the relationship of ICV to X differs between boys and girls, you might want to control ICV separately for each group.
The results after controlling for ICV are those brain regions/volumes/thickness that are not explained by ICV. If ICV and region X are highly correlated and region X is related to your independent variable, then you would conclude that that region is related, whereas it could be due to ICV. Additionally, there are probably a number of regions highly correlated with ICV, which make them potentially less interesting.
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On Mon, Jan 24, 2011 at 11:59 AM, Ilana Hairston hairstonster@gmail.com wrote:
Hi there, This is a bit outside the pure technical questions. My subject pool has both boys and girls, with the boys having larger intracranial volume. My results when controlling for gender and intracranial volume however are not the same (obviously, one is a dichotomous variable, the other continuous). Looking at the results, i prefer the latter over the former, more consistent with the literature, and more internally consistent (i.e., brain regions associated with intenalizing sub-scales and the internalizing total scale). But it could be argued that I am removing important variance - maybe stressed out kids have smaller heads?
Any recommendation?
thanks
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