In a 2-group RCT with one baseline and 2 follow-up assessment time-points, assume that
(i) follow-up outcomes are missing at random
(ii) relatively strong auxillary variables are available
My question is: Which is a better modelling approach?
(i) mixed-effects modelling (which treats baseline outcome as a covariate)
(ii) ANCOVA after multiple imputation at each follow-up timepoint
I have understood that method i (mixed-effects modelling) is generally sufficient without the need for imputation. But just how strong should the auxillary variable(s) be before method ii becomes a competitive approach?
Any guidance on this would be greatly appreciated.
