Vance W Berger1, Rebecca Agnor2. 1. National Cancer Institute and Biometry Research Group, University of Maryland Baltimore County, 9609 Medical Center Drive, Rockville, MD, 20850, USA. 2. Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina-Chapel Hill, Chapel Hill, NC, 27599, USA. rcagnor@live.unc.edu.