1. a Department of Applied Mathematics , Chung Yuan Christian University , Chung Li , Taiwan
2. b Division of Biostatistics and Bioinformatics , Institute of Population Health Sciences, National Health Research Institutes , Zhunan Town , Miaoli County , Taiwan
3. c Department of Biostatistics and Bioinformatics , Duke University School of Medicine , Durham , North Carolina , USA
4. d Division of Clinical Trial Statistics , Institute of Population Health Sciences, National Health Research Institutes , Zhunan Town , Miaoli County , Taiwan