Bibliographical noteFunding Information:
Bradley P. Carlin is Professor, Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN 55455. Thomas A. Louis is Senior Statistician, The RAND Corporation, Santa Monica, CA 90407. The first author’s work was supported in part by National Institute of Allergy and Infectious Diseases (NIAID) grant R01-A141966 and by National Institute of Environmental Health Sciences (NIEHS) grant 1- R01-ES07750; the second author’s work was supported in part by NIEHS grant 1-R01-ES07750 and NIAID contract N01-AI05073. The authors thank the editor and Dr. Melanie Wall for helpful comments that improved the manuscript.