1. Department of Statistics, School of Physical Sciences, Shahjalal University of Science and Technology, Sylhet, Bangladesh;
2. School of Distance Education, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia;
3. School of Industrial and System Engineering, Telkom University, Bandung, Indonesia;
4. School of Mathematical Sciences, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia