1. Department of Biostatistics; University of Florida; Gainesville FL 32611 U.S.A.
2. Pfizer BioTx Clinical Research; 35 Cambridge Park Dr. Cambridge MA 02140 U.S.A.
3. Department of Biostatistics; University of North Carolina; Chapel Hill NC 27599 U.S.A.
4. Geriatric Research; Malcom Randall VA Medical Center; Gainesville FL 32608 U.S.A.
5. Department of Health Outcomes and Policy; University of Florida; Gainesville FL 32611 U.S.A.