1. From the Statistics and Consulting Unit, Department of Mathematics and Statistics, Boston University, Boston, Mass (M.F.E., P.K.E., R.B.D.); Department of Psychology, University of Maine, Orono (M.F.E.); Department of Biostatistics, School of Public Health (L.M.S., A.B.), and Department of Neurology and Center for Neuroscience (C.D.), University of California-Davis; and Department of Neurology, Boston University School of Medicine, Boston, Mass (R.A., P.A.W.).