Institute of Statistics, National Tsing Hua University, Hsin-Chu, Taiwan.|Institute of Statistics, National Tsing Hua University, Hsin-Chu, Taiwan.|Division of Biostatistics and Bioinformatics, Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Taiwan.|Division of Biostatistics and Bioinformatics, Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Taiwan. rchung@nhri.org.tw.