Interpreting main effects in long. mixed model when interactions w/ time are in model

jax

New Member
#1
I am running a mixed effects longitudinal model with linear and quadratic time effects and a continuous outcome. I have a covariate that has a significant interaction with time-squared, so obviously the linear interaction and its main effect are left in the model. When interactions are in the model you cannot directly interpret lower order terms. I have centered time at the study mid point and would like to know if there are significant differences between the two levels of this covariate either on average or at the mid-point. When I include the code: lsmeans sex/ diff = control ('0'') ; does this give me the difference between males and females on average or at the time intercept, or neither? (time is continuous so I cannot include the interaction).

Any help would be greatly appreciated!