[R-sig-ME] Random slope with cross-level interaction

[Yashree Mehta]

Hi,

I have the following model:

Production = seed + fertilizer + fertilizer : wheatlanduse + (1 +
fertilizer | Household)

As the formula indicates, the household level is specified as the random
intercept. Fertilizer is specified as random slope , and has also been
specified as a fixed effect.

I am interested in cross-level interaction between fertilizer and the
wheatlanduse variable. So, I have inserted "fertilizer : wheatlanduse".

My question is: Do I have to include "wheatlanduse" as a main effect in the
formula as well? Or is it acceptable to only have it as a part of the
interaction term?

Thank you,

Regards,
Yashree

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