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Hi, yes thats right...the thing is that at the second level what I get is that the output of contrast A: [1 0] (mean covariate) is equal to the output of contrast B: [0 1] (mean covariate) how can this be true? Cheers On Wed, May 2, 2012 at 2:31 PM, Eugene Duff <[log in to unmask]> wrote: > Hi David - > > I'm having a bit of trouble following your description. > > I think your first-level copes are contrasts A: -1 0 1 and B: 1 0 -1. > Then, cope image B will simply be cope A*-1, and a group-level contrast of, > say, 1 0 for A will produce identical results to a group level contrast of > -1 0 for B. There will only be perfect correspondence between A and B > contrasts maps in these cases. The first level contrast B is not > completely necessary as you can define the negative contrasts at the group > level (although of course you will often be interested in the single > subject thresholded maps). > > I hope that helps a bit.. > > Eugene > > > > > On 2 May 2012 13:41, David Soto <[log in to unmask]> wrote: > >> HI, >> >> I may be missing something but can not figure out this >> >> I have a higher level analyses -one sample t test with covariate- >> performed on two copes from a first-level analyses. Each cope is >> the output of a linear contrast that goes A: -1 0 1 and B: 1 0 -1 >> respectively. For A, the MEAN output of the higher level analyses >> would give me a cluster that is identical to the one I get for B in the >> COVARIATE output >> of the higher level analyses. >> >> I understand in this test the MEAN output corresponds to stats where the >> effect of the COVARIATE is removed >> but why does the output looks the same in both? >> >> hopefully this is a rather trivial question! >> >> Cheers >> >> >