[R-sig-ME] Interaction terms with random slopes

[Yashree Mehta]

Hi,

I have the following question:

I estimate a random intercept-random slope model. For my research question,
I want to interact the random slope variable with another level-1
variable(which is not necessary as a main effect in the model). I am
interesting in observing whether this level-1 variable moderates the random
slope on the dependent variable.

Do I have to include the level-1 variable as a main effect in the model (as
is required by some linear modelling literature)? I would prefer not to
include this level-1 variable as a main effect due to problems of
multicollinearity.

Thank you very much!

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