1. Institute of Statistical Science; Academia Sinica; Taipei 11529 Taiwan
2. Graduate Institute of Epidemiology and Preventive Medicine; National Taiwan University; Taipei 10055 Taiwan
3. Division of Biometry; Institute of Agronomy, National Taiwan University; Taipei 10764 Taiwan
4. Division of Clinical Sciences; Center for Drug Evaluation; Taipei 11557 Taiwan
5. Biostatistics Section, Clinical Protocol Office; Koo Foundation Sun Yat-Sen Cancer Center; Taipei 11259 Taiwan