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Hi Fadel - So you mean a model with just the two group means as inputs, modelling the differences? Or just subtracting the copes? No these aren't appropriate approaches. Cheers, Eugene On 19 May 2011 17:28, Fadel Zeidan <[log in to unmask]> wrote: > Hi. > > Thanks for your response. > > My main question is, can I compare to higher level analyses in a within > subjects fashion. > > I have a group average for Time 1 before an intervention and another for > after the intervention. > > I want compare them directly and I have by simply comparing their > respective copes in FEAT. Can this be justified without being too liberal in > my stats? > > Thanks so much! > > > On 5/19/11 12:10 PM, "Eugene Duff" <[log in to unmask]> wrote: > > Hi Fadel - > > Are you saying your a comparing paired and unpaired t-tests? I suspect > there is something wrong with the model if the paired t-test images are > coming out speckled. > > Eugene > > On 19 May 2011 16:16, Fadel <[log in to unmask]> wrote: > Simply put: Can I compare to third level analyses in a within subjects > fashion. > > There were two conditions in MRI session 1. Subjects performed a task > (manipulation) and did not (rest). > I have the group effect for these contrasts corresponding to MRI 1. > > Subjects then participated in an intervention. > > > There were two conditions in MRI session 2 (after the intervention). > Subjects performed a task (manipulation) and did not (rest). > I have the group effect for these contrasts corresponding to MRI 2. > > Am I being too liberal? Am I treating within subject variability as between > subject variability? The analysis comes out beautifully. I also ran a > paired-t test with the same data, and the images come out speckled. I've > checked for outliers and have reran the analyses dozens of times to no > avail. > > Thanks. > >