1. Department of Health Science, College of Life Sciences, Brigham Young University, Provo, Utah, USA
2. Biostatistics Branch, and
3. Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
4. Westat, Durham, North Carolina, USA
5. Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland, USA