Dear Karl,
>
>> How can we do the subtraction A - B when A and B are acquired in
>> different sessions from one subject ? I heard that there could be a
>> problem with the global scaling if A and B are not acquired in the same
>> session.
>
>At the second level this should not be a problem (the data are globally
>normalised at the first level). To compare A and B, relative to rest,
>simply perform a two sample t test on the contrasts [1 -1] and [1 -1]
>from the first level (i.e. A-R - B-R = A-B).
>
thank you for your help. One question regarding the subtraction A-R - B-R:
What is the difference here between performing the two-sample t test on
the contrasts [1 -1] and [1 -1] (from the first level analysis) or
performing
it on the first level contrasts [1 0] and [1 0] ?
Thank you
Thomas Stephan
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Thomas Stephan Email: [log in to unmask]
Klinikum Grosshadern
Neurologisches Forschungshaus
Marchioninistr. 23 Fon: +49 089 / 7095-4819 *NEU*
81377 Muenchen Fax: +49 089 / 7095-4801
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