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Copula‐based regression models for a bivariate mixed discrete and continuous outcome
Author(s) -
de Leon A. R.,
Wu B.
Publication year - 2010
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.4087
Subject(s) - copula (linguistics) , bivariate analysis , covariate , econometrics , joint probability distribution , marginal distribution , marginal model , regression , mathematics , statistics , regression analysis , computer science , random variable
This paper is concerned with regression models for correlated mixed discrete and continuous outcomes constructed using copulas. Our approach entails specifying marginal regression models for the outcomes, and combining them via a copula to form a joint model. Specifically, we propose marginal regression models (e.g. generalized linear models) to link the outcomes' marginal means to covariates. To account for associations between outcomes, we adopt the Gaussian copula to indirectly specify their joint distributions. Our approach has two advantages over current methods: one, regression parameters in models for both outcomes are marginally meaningful, and two, the association is ‘margin‐free’, in the sense that it is characterized by the copula alone. By assuming a latent variable framework to describe discrete outcomes, the copula used still uniquely determines the joint distribution. In addition, association measures between outcomes can be interpreted in the usual way. We report results of simulations concerning the bias and efficiency of two likelihood‐based estimation methods for the model. Finally, we illustrate the model using data on burn injuries. Copyright © 2010 John Wiley & Sons, Ltd.