1. Guanghua School of Management, Peking University, Beijing 100871, People's Republic of China
2. Center of Statistical Research, Southwestern University of Finance and Economics, Chengdu 611130, People's Republic of China
3. School of Statistics, Southwestern University of Finance and Economics, Chengdu 611130, People's Republic of China
4. Center for Statistical Science, Peking University, Beijing 100871, People's Republic of China
5. Yuanpei College, Peking University, Beijing 100871, People's Republic of China