1. Research Administration and Development, University of Limpopo, Polokwane 0727, South Africa
2. Department of Public Health Medicine, University of Limpopo, Private Bag X1106, Sovenga, Polokwane 0727, South Africa
3. Department of Statistics and Operations Research, University of Limpopo, Polokwane 0727, South Africa
4. Department of Mathematics and Statistics, University of Maryland Baltimore County, Baltimore, MD 21250, USA
5. Faculty of Health Sciences, University of Limpopo, Polokwane 0727, South Africa
6. Non-Communicable Diseases Research Unit, South African Medical Research Council, Cape Town 7505, South Africa