Dear SPM experts,
I am using a flexible factorial design to run a mixed repeated-measures Anova. I would like to be sure that my design is correct, so any validation/invalidation of the following steps is more than welcomed.
I am doing a reward task. I have 3 groups of participants and 2 repeated conditions: valence (2 levels: gain, loss)) and magnitude (4 levels: 5$, 1$, 0.2$, 0$)).
I would like to see the main effects of the conditions, the interaction Condition1*Condition2, Group*Condition1, Group*Condition2 and Group*Condition1*Condition2.
I would have 4 factors:
Factor 1: Subject (69 subjects, independance = yes ; variance = equal)
Factor 2: Groups (3 groups with 25 / 22 / 22 subjects per group ; independance = yes ; variance = unequal)
Factor 3: Condition 1 (2 levels, independance = no ; variance = equal)
Factor 4: Condition 2 (4 levels, independance = no ; variance = equal)
I would specify 4 main effects and 4 interactions:
Main Effect 1 --> factor 1
Main Effect 2 --> factor 2
Main Effect 3 --> factor 3
Main effect 4 --> factor 4
Interaction 1 --> factor 3 and 4
Interaction 2 --> factor 2 and 3
Interaction 3 --> factor 2 and 4
Interaction 4 --> factor 2 and 3 and 4
I have an issue with the factor matrix, since I understood it can only have 4 columns.
Is a three-way interaction Group*Condition1*Condition2 impossible to compute in SPM?
If not, if I want to see the interaction Condition1*Condition2, should I remove the Group factor, and the factor matrix would look like:
Column 1: 1s
Column 2: subjects
Column 3: Condition1
Column 4: Condition2?
Also, when running the flex design, can I use the "beta*.img" from first-level analyses instead of "con*.img"?
Thank you so much for your time and your advices.
Best regards
Caroline
|