1. Texas Institute for Measurement, Evaluation, and Statistics and Department of Basic Vision Sciences, College of Optometry; The University of Houston; Houston TX 77204 U.S.A.
2. Department of Biostatistics; The University of Texas Health Science Center at Houston; Houston TX 77030 U.S.A.
3. Department of Biostatistics; The University of Kansas Medical Center; Kansas City KS 66160 U.S.A.
4. Alzheimer's Disease and Memory Disorders Center, Department of Neurology; Baylor College of Medicine; Houston TX 77030 U.S.A.