1. Dept. of Statistics, GC Univ., Lahore 54000, Pakistan
2. Department of Statistics, Faculty of Science, King Abdul Aziz University, Jeddah 21551, Saudi Arabia (Corresponding Author), e-mail: aslam_ravian@hotmail.com
3. Dept. of Industrial Management, National Taiwan Univ. of Science Technology, Taipei, Taiwan
4. Dept. of Industrial and Management Engineering, POSTECH, Pohang, Republic of Korea