Hello,
I would like to set up a repeated measures 2x2 anova at the second level
and examine the interaction. I have two groups of subjects (group 1 and
2) and each subject did 2 tasks (task A and B). The repeated measure
would be the tasks (2 levels). I would like to ask the question: are
there any task by group interactions ? I have set up things as
described below and I have a few questions.
I already have the COPE images for every subjects and task. I was
thinking of setting up the second level analysis as follows (with
smaller number of subjects for simplification). Each row represents a
COPE image from one subject.
group EV1 EV2 EV3 EV4
group_1_task_A_subj1 1 1 1 1 1
group_1_task_A_subj2 1 1 1 1 1
group_1_task_A_subj3 1 1 1 1 1
group_1_task_A_subj4 1 1 1 1 1
group_2_task_A_subj1 2 1 -1 -1 1
group_2_task_A_subj2 2 1 -1 -1 1
group_2_task_A_subj3 2 1 -1 -1 1
group_1_task_B_subj1 1 -1 1 -1 1
group_1_task_B_subj2 1 -1 1 -1 1
group_1_task_B_subj3 1 -1 1 -1 1
group_1_task_B_subj4 1 -1 1 -1 1
group_2_task_B_subj1 2 -1 -1 1 1
group_2_task_B_subj2 2 -1 -1 1 1
group_2_task_B_subj3 2 -1 -1 1 1
EV1 models task, EV2 models effects of group membership, EV3 the group x
task interaction, and EV4 is the grand mean.
The contrasts that I am thinking of implementing are as follows:
1 2 3 4
C1 1 0 0 0
C2 0 1 0 0
C3 0 0 1 0
and the F-tests are (with their interpretation)
F1 F2 F3
C1 on off off - main effect of task
C2 off on off - main effect of group
C3 off off on - interaction between the two factors
Question: is the repeated measures factor (task) the same as considering
this variable as fixed and the other factor (group) as random ? I
believe the F-tests above will not give me the exact test that I want
but I am not sure.
Thanks in advance,
Arun
