The Max-CUSUM Chart
Keoagile Thaga, Smily Cheng
Department of Statistics, University of Botswana, Gaborone, Botswana; Department of Statistics, University of Manitoba, Winnipeg, MB, Canada

Control charts have been widely used in industries to monitor process quality. We usually use two control charts to monitor the process. One chart is used for monitoring process mean and another for monitoring process variability, when dealing with variables data. A single Cumulative Sum (CUSUM) control chart capable of detecting changes in both mean and standard deviation, referred to as the Max-CUSUM chart is proposed. This chart is based on standardizing the sample means and standard deviations. This chart uses only one plotting variable to monitor both parameters. The proposed chart is compared with other recently developed single charts. Comparisons are based on the average run lengths. The Max-CUSUM chart detects small shifts in the mean and standard deviation quicker than the Max-EWMA chart and the Max chart. This makes the Max-CUSUM chart more applicable in modern production process where high quality goods are produced with very low fraction of nonconforming products and there is high demand for good quality.

Keywords: Cusum; Out of control; Single charts

Biography: Professor Keoagile Thaga holds a Bachelor of Statistics Degree from University of Botswana, Master of Science Degree in Statistics and a PhD in Statistical Quality Control from University of Manitoba in Canada. He is an Associate Professor of Statistics in the University of Botswana. Professor Thaga has researched and published extensively in Statistical Quality Control. Professor Thaga has done consultancy projects on population issues and HIV and AIDS in Botswana. Professor Thaga has made significant contribution in the key areas of research and publications. He has published in refereed regional and international journals in the field of Statistical quality control, gender, sports and nutrition.

Across the above research areas, Professor Thaga has, to date, published 14 articles in refereed journals; 1 book chapter, 3 published conference proceeding; 8 unpublished conference proceedings and 1 module for Statistics for Development Workers.