Hello,
I am creating a GLM to model between weight dependent between twin differences across a sample of monozygotic and dizygotic twins. I am having trouble figuring out how to set up the matrix to include EVs for each twin pairs & zygosity without creating collinearity.
This is an abbreviated example of my matrix:
Group EV1 EV2 EV3 EV4 EV5
1 BMI level Pair1 Pair2 Pair3 Zygosity *(0=MZ, 1=DZ)
Input1 1 1 1 0 0 0
Input2 1 -1 1 0 0 0
Input3 1 1 0 1 0 1
Input4 1 -1 0 1 0 1
Input5 1 1 0 0 1 0
Input6 1 -1 0 0 1 0
My contrast of interest is:
EV1 EV2 EV3 EV4 EV5
HighBMI > Low BMI 1 0 0 0 0
I think the collinearity warning is given since the pair EV and zygosity EV are the same for both twins in a pair.
Does anyone know a good way to set up theGLM matrix to avoid this problem?
Thanks for your help!
Jenny
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