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Hi On 13 Feb 2008, at 22:19, Joseph T. Devlin wrote: > Hi Yvonne, > > Since no one more statistically savvy than me has answered as yet, > I'll poke my head out and say "no" -- FSL doesn't offer an > implementation of the "minimum statistic" implementation of > conjunction analyses. To be honest, though, there are real > problems with interpreting those statistic values, as pointed out > by Tom Nichols and colleagues. In many cases it is sufficient to > use inclusive masking. If the contrasts are truly orthogonal, then > you can reasonably multiply the p-values together to get a > "conjunction" p-value in a given voxel. For instance, if you were > interested in areas in Group 1 where A>B and masked it with Group > 2's A>B (at p<0.001 uncorrected to pick a random threshold...), > then any areas at p<0.001 in the G1 A>B contrast that are also > present in G2 A>B are unlikely to be there by chance given that the > corresponding p-value would be p<10^-6. > Just to note that even this is a bit misleading, because p<10^-6 refers to the null hypothesis that NEITHER of the activations were present - you certainly can't claim a conjunction with this p-value. I agree with Joe that just showing the overlap is fine. T > Personally, I wouldn't feel the need to see a computed p-value -- > it would be sufficient to know that the "conjunction" contrasts > were truly orthogonal and know the level that each one was >