Dear fsler,
I have questions about my 2x2 ANOVA interaction. I have two main effects: diagnosis group (patient and control ) and age (young and old). There are 2 subjects in each subgroup which makes 8 subjects in total. The design matrix of ANOVA looks like following
age diagnosis interaction mean
1 1 1 1
1 1 1 1
1 -1 -1 1
1 -1 -1 1
-1 1 -1 1
-1 1 -1 1
-1 -1 1 1
-1 -1 1 1
contrast:
F1 F2 F3
C1 1 0 0 0 X
C2 0 1 0 0 X
C3 0 0 1 0 X
C4 -1 0 0 0
C5 0 -1 0 0
C6 0 0 -1 0
The significant brain activities were found on all three F contrasts which means significant brain activity between age, diagnosis and age by diagnosis interaction. As interaction showed significant in my model, I further checked t-test that it is a negative interaction. How could I explain the result? Do I need to run other four separated one way ANOVA within the ROI indicated by interaction results to confirm the resource of interaction?
Thanks very much in advance.
Joyce
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