Hi - what you're suggesting might be ok - maybe some extra insight can
be found in our related example in the manual at:
http://fsl.fmrib.ox.ac.uk/fsl/feat5/detail.html#ANOVA3factors2levels
Or you might find it easier not to think of this as an ANOVA but as a
GLM, modelling the different combination of conditions (which I
suspect is actually very close to the way that you are modelling this
in your email).
Cheers.
On 14 Jan 2009, at 13:43, Jan Derrfuss wrote:
> Dear All,
>
> I am currently analyzing a slightly unusual design which I'm not
> completely
> sure how to set up in FSL. The design is an incomplete 2x2x2-factorial
> design. The design was blocked with all 6 conditions performed
> within one
> run in counterbalanced order.
>
> What I've done is the following: There are 6 EVs per subject,
> specifying the
> onsets of the 6 conditions. The EVs represent the following factor-
> level
> combinations:
> EV1 = A1B1C1
> EV2 = A2B1C1
> EV3 = A1B1C2
> EV4 = A2B1C2
> EV5 = A1B2C1
> EV6 = A2B2C1
>
> I set up the following contrasts (for brevity, I skip the reverse
> contrasts):
> A1 vs. A2: 1 -1 1 -1 1 -1
> B1 vs. B2: 1 1 0 0 -1 -1
> C1 vs. C2: 1 1 -1 -1 0 0
> Interaction AxB: 1 -1 0 0 -1 1
> Interaction AxC: 1 -1 -1 1 0 0
> (interactions display areas with overadditive activation)
>
> My questions are:
> - Is it possible to set up the analysis this way?
> - I noticed that the 2007 course slides suggest a different way to
> set up a
> 2x2-factorial design (EV1 models A1, EV2 models B1, EV3 models the
> interaction, F tests are conducted). Would this be a better way or an
> alternative way? If this approach were to be preferred, how would I
> have to
> adapt it to my design?
>
> Any help would be greatly appreciated.
>
> Cheers,
> Jan
>
---------------------------------------------------------------------------
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
---------------------------------------------------------------------------
|