AN INFLUENCE APPROACH FOR SENSITIVITY ANALYSIS OF NON-RANDOM DROPOUT BASED ON THE COVARIANCE STRUCTURE*

Abstract – A generalized Heckman model is used for the joint modeling of longitudinal continuous responses and dropout in order to see the influence of a small perturbation of the elements of the covariance structure on displacement of the likelihood. The perturbation from random dropout in the direction of informative dropout is considered for Mastitis data