243 – Methods for Longitudinal Data Analysis
Small Sample GEE Estimation of Regression Parameters for Longitudinal Data
Sudhir Paul
University of Windsor
Xuemao Zhang
Lakehead University
Generalized estimating equations (GEE) is a widely used method to estimate marginal regression parameters for correlated responses. The advantage of the GEE is that the estimates of the regression parameters are asymptotically unbiased even if the correlation structure is misspecified, although their small sample properties are not known. In this paper, two bias corrected GEE estimators of the regression parameters in longitudinal data are proposed when the number of subjects is small and the number of observations on each subject is fixed. Simulations show that both methods do well in reducing bias and have, in general, higher efficiency than the GEE estimates.