Dear Margaret,
> thanks for the message...
> can you describe briefly the steps to do this multi-subjects conjunction
> analysis in spm99?
This is simple. Set up and estimate your model and then, in 'results'
specify a series of contrasts that you want to enter into a
conjunction. A conjunction analysis is then performed when you select
more than one contrast (the contrasts you want a conjuncion over). To
select more than one contrast hold down Control Key whilst selecting
with the mouse in the Contrast Manager. The ensuing SPM will be a
conjunction SPM with appropriate corrected and uncorrected P values.
Generally you should choose a very low threshold for conjunction
analyses (e.g. p<0.5 to p<0.05).
For multi-subject conjunctions simply specify the number of
sessions/subjects and SPM will build the appropriate design matrix.
When it comes to specifying the constrasts enter the contrast of
interest for each session/subject separately with 0s elsewhere so you
have the same number of contrasts as subjects.
With best wishes - Karl
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