EWMA Dispersion Control Charts for Normal and Non‐normal Processes |
| |
| Authors: | Saddam Akber Abbasi Muhammad Riaz Arden Miller Shabbir Ahmad Hafiz Zafar Nazir |
| |
| Affiliation: | 1. Department of Mathematics and Statistics, King Fahd University of Petroleum and Minerals, Dhahran, KSA;2. Department of Statistics, The University of Auckland, Auckland, New Zealand;3. Department of Mathematics, COMSATS Institute of Information Technology, Wah Cantt, Pakistan;4. Department of Statistics, University of Sargodha, Sargodha, Pakistan |
| |
| Abstract: | Process monitoring through control charts is a quite popular practice in statistical process control. This study is planned for monitoring the process dispersion parameter using exponentially weighted moving average (EWMA) control chart scheme. Most of the EWMA dispersion charts that have been proposed are based on the assumption that the parent distribution of the quality characteristic is normal, which is not always the case. In this study, we develop new EWMA charts based on a wide range of dispersion estimates for processes following normal and non‐normal parent distributions. The performance of all the charts is evaluated and compared using run length characteristics (such as the average run length). Extra quadratic loss, relative average run length, and performance comparison index measures are also used to examine the overall effectiveness of the EWMA dispersion charts.Copyright © 2014 John Wiley & Sons, Ltd. |
| |
| Keywords: | ARL control charts dispersion parameter EQL normality/non‐normality PCI RARL |
|
|
