Modelling heterogeneity in longitudinal binomial responses by generalized estimating equations

ABSTRACT

Extra-binomial variation in longitudinal/clustered binomial data is frequently observed in biomedical and observational studies. The usual generalized estimating equations method treats the extra-binomial parameter as a constant across all subjects. In this paper, a two-parameter variance function modelling the extraneous variance is proposed to account for heterogeneity among subjects. The new approach allows modelling the extra-binomial variation as a function of the mean and binomial size.