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Dear all,
I have a question regarding Glm contrasts,
We propose the following analysis:
We have two groups and a continuous variable and we want to know whether there is a greater correlation in a group compared to the other.
My EV's are:
EV1--> the control group,
EV2--> the patient group,
EV3--> the variable for controls,
EV4--> the variable for patients.
The design matrix is:
The contrasts that we want to test are:
0 0 1 -1 - (because we want to see if the correlation is more significative in controls vs patient)
1 -1 1 -1 - (I think this contrast means if the correlation is more positive in controls compared to patients)
However, in the last contrast, in addition to the effect that we are testing, there is another effect that is "confounded": whether the correlation is more negative in the patient's group compared to the control's group. This effect is not a problem for my hypothesis but what i would like to know is whether the second contrast is correct in order to test what we have explained.
Silvia