Thank you for your answer!
So if I understand well, I have to construct my design matrix like that:
ex design (here for 4 subjects), with the EV6 corresponding to plasma level (demeaned) for exemple:
EV1 EV2 EV3 EV4 EV5 EV6
1 1 0 0 0 2
1 0 1 0 0 1.5
1 0 0 1 0 -0.6
1 0 0 0 1 3
-1 1 0 0 0 4
-1 0 1 0 0 2.4
-1 0 0 1 0 1.2
-1 0 0 0 1 3
And then, as contrast, I create:
EV1 EV2 EV3 EV4 EV5 EV6
C1 Condition A>B 1 0 0 0 0 0
C2 Condition B>A -1 0 0 0 0 0
C3 positive effect of plasma level 0 0 0 0 0 1
C4 negative effect of plasma level 0 0 0 0 0 -1
And thus, if I want to look at the difference between A and B that is correlated to the plasmatic level of the drug, I have to consider the contrasts C3 and C4?
Thank you in advance for your reply!
Carole
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