Hi,
there was no attachment but yes.
And yes, you can include a covariate but you need to form the interaction with each EV separately and form a F-test across these.
Cheers,
Andreas
Am 31.07.2015 um 16:17 schrieb "Huffmeijer, R." <[log in to unmask]>:
> Hi Andreas,
>
> Thanks for your answer!
>
> If we understand correctly, we could use cope images as inputs for the higher level analyses, define EVs for each cope and subject, and then define the f-tests (see attached for a simple example with 3 subjects). Is this correct?
>
> We have one more question, though: We would also like to include a covariate (a personality characteristic) and test the interaction between stimulus type and the covariate. Would it be possible to add a covariate to this model as well?
>
> Thanks,
> Esther and Renske
>
>
> -----Original Message-----
> From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf Of Andreas Bartsch
> Sent: donderdag 30 juli 2015 21:03
> To: [log in to unmask]
> Subject: Re: [FSL] F-test
>
> Hi,
>
> no - you can't pass F-contrasts to higher levels directly. Passing VARCOPEs up to a group level is based on t-test contrasts - the group stats framework cannot deal with passing up of f-test contrasts as not all of the assumptions would stand.
> However, you use the COPEs of the lower level F-test (i.e. the COPEs that go into the lower lvel F-test) and then do an F-test at the higher level.
>
> You may also consider using a type of summary stats of your COPEs of interest, i.e. the root-mean-squared (RMS) of the COPEs, and pass them up to the higher level using randomise.
> Cheers,
> Andreas
>
>
>
> Am 30.07.15 16:19 schrieb "FSL - FMRIB's Software Library on behalf of Esther Heckendorf" unter <[log in to unmask] on behalf of
> [log in to unmask]>:
>
>> Hi,
>>
>> We have a small question about using an F-test in FEAT. We've shown
>> participants three different types of stimuli (S1, S2 and S3) and would
>> like to test the main effect of stimulus type. We have no specific
>> hypotheses regarding the direction of effects. In the lower level
>> analysis we have included contrasts comparing each pair of stimuli
>> (i.e.,
>> S1 vs S2, S1 vs S3, and S2 vs S3), as well as an F-test across two of
>> these contrasts (S1 vs S2 and S2 vs S3) to test the 'entire' main
>> effect in one test. When setting up a higher level analysis to test the
>> significance of the effects in the entire group of subjects we could
>> only include the contrasts comparing each pair, but not the F-test.
>> That's of course a bit of a problem, as we would like to check the
>> significance of the 'entire' main effect before performing individual
>> comparisons. Is it possible to include the F-test in the higher level analysis somehow?
>>
>> Thanks!
>> Esther
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