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Hi - this will be rank deficient - so I would instead follow the examples in the FEAT manual - see for example the 'triple-t-test' example. Cheers. On 6 Aug 2009, at 12:32, Martin M Monti wrote: > Illuminated FSL masters, > > I am following a patient longitudinally, on a series of different > tasks. > > Say the design is 1 subject performing 2 tasks each repeated 4 times. > > Would this set-up be correct? > > EV1: Overall subject mean [is this actually needed?] > EV2: Task1 mean > EV3: Task2 mean > EVs4-7: Task1_T0 (reference group), Task1_T1, Task1_T2, Task1_T3 > EVs8-11: Task2_T0 (reference group), Task2_T1, Task2_T2, Task2_T3 > > (visually..) > Input File > [Task1 T0] 1 1 0 0 0 0 0 0 0 0 0 > [Task1 T1] 1 1 0 0 1 0 0 0 0 0 0 > [Task1 T2] 1 1 0 0 0 1 0 0 0 0 0 > [Task1 T3] 1 1 0 0 0 0 1 0 0 0 0 > [Task2 T0] 1 0 1 0 0 0 0 0 0 0 0 > [Task2 T1] 1 0 1 0 0 0 0 0 1 0 0 > [Task2 T2] 1 0 1 0 0 0 0 0 0 1 0 > [Task2 T3] 1 0 1 0 0 0 0 0 0 0 1 > > Contrasts & F-tests would be as follows: > > C1: 0 0 0 0 1 0 0 0 0 0 0 F1 (i.e. EV5) > C2: 0 0 0 0 0 1 0 0 0 0 0 F1 (i.e. EV6 ) > C3: 0 0 0 0 0 0 1 0 0 0 0 F1 (i.e. EV7) > > C4: 0 0 0 0 0 0 0 0 1 0 0 F2 (i.e. EV9) > C5: 0 0 0 0 0 0 0 0 0 1 0 F2 (i.e. EV10) > C6: 0 0 0 0 0 0 0 0 0 0 1 F2 (i.e. EV11) > > > Contrasts & Ftests interpretations: > > F1 is the within subject effect for Test1 > F2 is the within subject effect for Test2 > Each contrasts is essentially like a Dunnett test (i.e. comparison > of each repetition to its reference group). However, without the > actual multiple comparisons correction of the Dunnett test > (considering the number of voxels tested a few multiple comparisons > are maybe not that big of an issue?!). > > Does this sound about right? > > cheers > > martin > --------------------------------------------------------------------------- Stephen M. Smith, Professor of Biomedical Engineering Associate Director, Oxford University FMRIB Centre FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK +44 (0) 1865 222726 (fax 222717) [log in to unmask] http://www.fmrib.ox.ac.uk/~steve ---------------------------------------------------------------------------