1. Department of Business Statistics and Operations Research, School of Economic Sciences, North West University, Mafikeng Campus, Mmabatho 2745, South Africa
2. Department of Information Sciences, School of Economic Sciences, North West University, Mafikeng Campus, Mmabatho 2745, South Africa
3. Department of Statistics and Operations Research, National University of Science and Technology, Ascot, Bulawayo P.O. Box AC 939, Zimbabwe