Extract average value within binary mask


I have run a seed-to-voxel connectivity analysis in CONN and have the resulting connectivity maps for each individual subject. I also have a significant connectivity cluster from the resulting group analysis. I want to extract the average connectivity value within the cluster (as well as the standard deviation) for each subject. I tried using

fslstats CONN_MAP.nii -k sig_mask.nii -m

, but apparently the cluster mask output by conn has different image dimensions than the connectivity map it outputs, so fslstats would not run. I am sure, despite the dimension mismatch, that the cluster maps well on the connectivity map. Anyone have suggestions to extract the average value here?


Of note, when I try to resample the mask to the statistical map, the location of the cluster changes.