Dear SPMers,
is anybody aware of if there is any valid (if possible published) way of comparing cluster extents of significant atrophy (as measured by VBM) from two different analyses (with the same degrees of freedom)?
For the statisticians: Would it be valid way to apply a proportions test comparing two proportions calculated as the amount of "activated" voxels devided by the total amount of tested voxels and to use the following information provided by the SPM stats to calculate the "sample sizes": "total number of resels"/("expected cluster extent in resels" * "number of expected resels")? The denominator would then scale the total number of resels by the total expected extent of activated resels at a given statistical threshold.
Thanks,
Juergen
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