Hi there,
Three questions all related to interaction. I realized that I really have
problems understanding the two-way interaction term in SPM.
1) I wanted to test common and uniquely activated regions between the main
effects. I read on the list and I heard from colleagues that uniquely or
differentially activated regions between two main effects should come out
in a two-way interaction. Is that correct??? Really don’t understand…
2) I have two factors A and B with two levels each, and consequently four
conditions: A1+B1,A1+B2, A2+B1, A2+B2. My interaction terms were: -1 1 1 -
1 and 1 -1 -1 1.What do I test here? I read something about “positive”
and “negative” interactions!???
3) Is it the case that I am allowed or even SHOULD use a more lenient
threshold for the interaction? Is there a convention?
Cheers,
Nicole
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