Hi Steve,
Thanks a lot for your reply. I grew interested in what I would get if I
would model the data differently and therefore adapted my EVs. Now I have:
EV1 = A on/off
EV2 = B on/off
EV3 = C on/off
EV4 = interaction AB
EV5 = interaction AC
I ran the 1st-level analysis with the following contrasts:
F F F F F
1 0 0 0 0 x
0 1 0 0 0 x
0 0 1 0 0 x
0 0 0 1 0 x
0 0 0 0 1 x
My problem right now is that I'm not really sure how to set up the 2nd-level
analysis. It would be really great if you - or somebody else - could point
me in the right direction.
Cheers,
Jan
>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
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