“…The models were extended by other colleages Daniels, 2007, 2008; Lee et al, 2009Lee et al, , 2010Lee et al, , 2011aLee et al, , 2011b; Lee and Mercante, 2010; Lee et al, 2013). These models have several advantages: (1) since marginalized models have two separate submodels (marginal mean and dependence models), the interpretation of the parameters in the marginal mean model is invariant with respect to specification of the dependence model; 2) estimation of the parameters in the marginal mean model is more robust to mis-specification of the dependence model (Heagerty and Zeger, 2000;Heagerty, 2002;Lee and Daniels, 2007;Lee and Mercante, 2010).…”