LLN, le 25/02/05
Dear All,
I'll be happy to hear our stat gurus on the contrasts proposed by Caroline.
>For the 1st level analysis, the following t- contrasts are created:
>
> 1. [-1 1 0] for A vs Rest
> 2. [-1 0 1] for B vs Rest
> 3. [0 1 0] for condition A
> 4. [0 0 1] for condition B
My understanding was that, as all conditions are explicitely
declared, contrasts 3 and 4 that are "conceptually" equivalent to 1
and 2 should not work because, as they do not sum to 0, there is
nothing left for SPM to compare them. I thought that 3 and 4 would
work only if Rest had not been explicitely declared. Am I right or
wrong?
> I know I am comparing different things in the 2nd level analysis,
>but what exactly are the differences between theses 6 comparisons?
>How to do a correct ANOVA?
If A and B are in the same run/session, there is maybe no need to
compare them through Rest. You could compute A-B at the 1st level and
take these con* files to the second level in a one-sample t test.
(Right?)
Yours,
Mauro.
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Mauro PESENTI
Research Associate, National Fund for Scientific Research (Belgium)
Unite de Neurosciences Cognitives
Departement de Psychologie
Universite Catholique de Louvain
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