Dear SPMers,
I am running a group X task ANOVA using the guidelines by Glascher and
Gitelman for flexible factorial designs. The design matrix includes main
effects of subject, group and task, and the interaction of group and task,
and the contrasts match those in the guidelines (design matrix and
guidelines attached).
For the F contrast for main effect of group the SPM_F image shows negative
values only. This does not affect other contrasts (e.g. main effect of
task). There is a cluster of strongly negative F values in a sensible
location, and this same cluster has positive F scores when I rerun the
ANOVA using full factorial (SPM_F images for flexible and full factorial
attached).
I want to stick with the flexible design, since it models subject effect
explicitly. Can anyone advise how to fix this?
Best wishes,
Paul Wright
--
Paul Wright PhD
Centre for Speech, Language, and the Brain
Dept. of Experimental Psychology Tel: +44 (0)1223 766559 University of
Cambridge Fax: +44 (0)1223 766452 Downing Street
email:[log in to unmask] Cambridge http://csl.psychol.cam.ac.uk CB3
2EB
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