1. Division of Biostatistics and Computing, Eastman Dental Center, 625 Elmwood Ave., Rochester, New York 14620
2. Task Force on Design & Analysis, Inc., 2975 Princeton Pike, Lawrenceville, New Jersey 08648, and Division of Biostatistics, School of Public Health, Columbia University
3. EODPP, NIDR, Westwood Building, Room 525, 5333 Westbard Ave., Bethesda, Maryland 20814