Hi Steve
This was a fixed effects second-level analysis (we have 5 sessions
for 6 subjects). Is your suggestion still the most likely explanation?
Thanks
Lori
On 18 Jan 2007, at 11:34, Stephen Smith wrote:
> Hi - this would depend on the exact details of what you've done,
> but 0.1% doesn't sound very high
> to me. However most likely the simple explanation is that you have
> used the default group-stats
> option of FLAME, which is more accurate than OLS (ordinary least
> squares) for the higher-level
> analysis, but the averaging that you have done yourself is
> equivalent to an OLS analysis, hence the
> difference?
>
> Cheers, Steve.
>
>
>
>
> On Thu, 18 Jan 2007 11:18:02 +0000, Lori Minini
> <[log in to unmask]> wrote:
>
>> Hello
>>
>> I have run Featquery (with analyze mask images) on a series of FEAT
>> higher-level folders generated in FSL 3.3, but that used first-level
>> analyses from FSL 3.2. I found differences (as big as 0.1%) between
>> the COPE % values of the higher-level analyses and the average of the
>> first-level results.
>>
>> I checked whether using first-level analyses from FSL 3.2 could have
>> generated this difference by comparing the Featquery results for
>> first-level analyses carried out in both FSL 3.2 and FSL 3.3 for the
>> same data. This resulted in some minor differences, however it seems
>> that they are unlikely to account for the discrepancy reported above
>> as this was also present for a subset of the data for which both
>> first- and higher-level analyses were run in FSL 3.3.
>>
>> Has anyone encountered a similar difference and do you know where it
>> stems from? In general, should we expect to find differences in the
>> Featquery results for higher-level analyses depending on the FSL
>> version used for the first-level?
>>
>> Many thanks
>>
>> Lori
>>
>>
>> _______________________________________________________
>>
>> Dr Lori Minini, PhD
>>
>> Department of Physiology, Anatomy and Genetics & FMRIB Centre
>> University of Oxford
>> Sherrington Building
>> Parks Road
>> Oxford OX1 3PT
>>
>> tel +44-1865-272555
>> fax +44-1865-272543
>> email [log in to unmask]
>>
>> _______________________________________________________
>> ===========================================================
> ==============
_______________________________________________________
Dr Lori Minini, PhD
MRC Postdoctoral Research Scientist
Department of Physiology, Anatomy and Genetics & FMRIB Centre
University of Oxford
Sherrington Building
Parks Road
Oxford OX1 3PT
tel +44-1865-272555
fax +44-1865-272543
email [log in to unmask]
_______________________________________________________
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