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On Nov 18, 2008, at 12:11 PM, J Labus wrote: > I have 2 groups of subject who underwent 4 conditions in an fMRI > study. I > want to show where activation in these 4 conditions correlates with a > continuous variable. I have an average measure of the continuous > variable > for each subject in each condition. I have been struggling to > specify the > appropriate second-level design. > > I chose 'full factorial" design and specified the scans representing > activity for each condition in each group. I specified group and > condition > as factors (8 total factors). I also specified the 1 covariate. > > The design does not produce the results I expected. I get a F > tests for > 1)avg effect of condition, 2)main effect of group,3) main effect for > condition, and 4) interaction between group and condition. > However, the > main effect of the covariate is not shown in the results manager. > > > It seems that the authors of SPM have chosen not to report the F > test of the > beta for the covariate in the results( although of course it has been > estimated). So if this is correct, what model should I be employing to > answer my question. > > Is it multiple regression? If so, if so i need to clarify 2 things. > 1)Do i > need 8 covariates with values for each relevant cell and zeros for > the 7 > other cells? Do i need to center the covariate across the 8 > conditions ahead > of time? > > Thank you for any help you can provide, > Jen > > >