1. Epidemiology Branch, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
2. Department of Statistics, Colorado State University, Fort Collins, Colorado, USA
3. Biostatistics Branch, NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA
4. Department of Mathematics and Statistics, University of North Carolina at Wilmington, North Carolina, USA
5. Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA