Hi,
I have two within subjects conditions, each one of them with 3 levels: cond1 (light,medium, dark), cond2 (F1,F2,F3). I want to test the effect of each individually and their interaction. I think I am ok with the subjects, condition1 and 2 but I am struggling to add into the design matrix the interaction effect (condition 1 * condition 2). Any help will be much appreaciated.
For simplicity, we will assume 3 subjects:
cond1 cond2
interaction
S1 Light F1 1 0
0 0 0 0
0
??
S2 Light F2 0 1
0 0 0 0
1
S3 Light F3 0 0
1 0 0 1
0
S1 Medium F1 1 0 0
0 1 0 0
S2 Medium F2 0 1 0
0 1 0 1
S3 Medium F3 0 0 1
0 1 1 0
S1 Dark F1 1 0
0 1 0 0
0
S2 Dark F2 0
1 0 1 0 0
1
S3 Dark F3 0
0 1 1 0 1
0
Contrast for condition1: [0,0,0,1,1,0,0,0,0]
Contrast for condition2:[0,0,0,0,0,1,1,0,0]
Contrast for interaction [0,0,0,0,0,0,0,1,1]
And exchange blocks: [1,2,3,1,2,3,1,2,3,1,2,3]
Thank you for your help!