Title :
An EWMA control chart for monitoring the mean of skewed populations using weighted variance
Author :
Khoo, Michael B C ; Atta, Abdu M A
Author_Institution :
Sch. of Math. Sci., Univ. Sains Malaysia, Penang, Malaysia
Abstract :
This paper discusses the use of weighted variance (WV) in setting up the limits of the exponentially weighted moving average (EWMA) chart for the monitoring of the mean of a process from a skewed population. This chart, called the WV-EWMA chart hereafter, reduces to the standard EWMA chart when the underlying distribution is symmetric. The Type-I and Type-II errors of the WV-EWMA chart are compared with that of the existing charts for skewed populations. Simulation results show that the new method gives a considerable improvement over the existing methods when the underlying distribution is skewed.
Keywords :
control charts; moving average processes; process monitoring; statistical process control; EWMA control chart; Type-I error; Type-II error; exponentially weighted moving average control chart; skewed population; weighted variance; Chemical processes; Condition monitoring; Control charts; Cutting tools; Distributed computing; Equations; Error correction; Gaussian distribution; Random variables; EWMA chart; Type-I error; Type-II error; X̄ chart; skewed populations; skewness correction; weighted standard deviation; weighted variance;
Conference_Titel :
Industrial Engineering and Engineering Management, 2008. IEEM 2008. IEEE International Conference on
Conference_Location :
Singapore
Print_ISBN :
978-1-4244-2629-4
Electronic_ISBN :
978-1-4244-2630-0
DOI :
10.1109/IEEM.2008.4737863
