1. Department of Epidemiology; College of Public Health; University of Nebraska Medical Center; Omaha Nebraska
2. Department of Allied Health Sciences; School of Medicine; University of North Carolina at Chapel Hill; Chapel Hill North Carolina
3. Department of Health Services Research and Administration; College of Public Health; University of Nebraska Medical Center; Omaha Nebraska
4. Center for Collaboration on Research Design and Analysis; College of Public Health; University of Nebraska Medical Center; Omaha Nebraska
5. Department of Biostatistics; College of Public Health; University of Nebraska Medical Center; Omaha Nebraska