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