GEE analysis of negatively correlated binary responses: a caution

The method of generalized estimating equations has become almost standard f or analysing longitudinal and other correlated response data. However, we h ave found that if binary responses have less than binomial variation over c lusters, and are modelled using exchangeable correlations, prevailing softw are implementations may give unreliable results. Bounding the negative corr elation away from its theoretical minimum may not always be a satisfactory solution. In such instances, using the independence working correlation str ucture and robust SEs is a more trustworthy alternative. Copyright (C) 2000 John Wiley & Sons, Ltd.