Hi Doug,

This is my main objective.

1. PET in Group 1 vs Group 2 

2. Thickness in the same sample, Group 1 vs Group 2

3. ASL in the same sample of Group 1 vs Group 2

4. Create a binary mask of the overlapping corrected sig voxels from 1-3.

5. This mask is therefore a site of co-localised atrophy, perfusion and PET changes in Group wrt Group 2.

Now, I would like to look at how the effect sizes of 1-3 compare against one another, above and beyond the spatial overlap.  I hope this is clearer, but let me know if I could provide more information. I thought about looking at Z-scores like some other studies, but I find that it is highly dependent on the range of the SD, which differed to a large extent (PET having a range of 1-10 vs 1-3 in atrophy). Hence I thought the Cohen's D might represent a more plausible workaround by pooling the SD across both groups, 

Thanks.

Best Wishes,

Elijah