Hi-

OK, the bi-sided vs 2-sided is selected in the initial Clusterize GUI that pops up; in this case, it won't have any effect on the F-stat, because it is always >=0.

I do think the difference is the t-stat is signed and clustered bi-sidedly; the F-stat is only positive, and can't distinguish between underlying positive and negative effects. Consider in the t-stats when there is a large, suprathreshold negative cluster with a couple positive, suprathreshold voxels touching it. In the bi-sided t-stat clusterizing, the clusterized output will only be made up of the negative voxels (in 2-sided clusterizing here, the output would be made up of both the positive and negative ones). In the "bi-sided F-stat" clusterizing---which is really just 1-sided clusterizing, because F>=0---the underlying sign differentiation is lost, so the clusterized output would be made up of all those voxels, because the t>0 and t<0 information has been lost.

To verify this, can I send you a Box link to get the statistics volume to look at?

thanks,
pt