Chong, J.K. and Teoh, W.L. and Khoo, Michael B.C. and Chong, Z.L. and Teh, S.Y.
(2016)
*Performance comparison of the exact run-length
distribution between the run sum X and EWMA X charts.*
Journal of Quality Measurement and Analysis, 12
(1-2).
pp. 11-26.
ISSN 1823-5670

PDF
Restricted to Registered users only 776kB |

Official URL: http://www.ukm.my/jqma/jqma12_1_2a.html

## Abstract

The run sum (RS) X and exponentially weighted moving average (EWMA) X charts are very effective in detecting small and moderate process mean shifts. The design of the RS X and EWMA X charts based on the average run length (ARL) alone, can be misleading and confusing. This is due to the fact that the run-length distribution of a control chart is highly right-skewed when the process is in-control or slightly out-of-control; while that for the out-ofcontrol cases, the run-length distribution is almost symmetric. On the other hand, the percentiles of the run-length distribution provide the probability of getting a signal by a certain number of samples. This will benefit practitioners as the percentiles of the run-length distribution give comprehensive information regarding the behaviour of a control chart. Accordingly, this paper provides a thorough study of the run-length properties (ARL, standard deviation of the run length and percentiles of the run-length distribution) for the RS X and EWMA X charts. Comparative studies show that the EWMA X chart outperforms the RS X charts for detecting small mean shifts when all the control charts are optimized with respect to a small shift size. However, the RS X charts surpass the EWMA X chart for all sizes of mean shifts when all the control charts are optimized with respect to a large shift size.

Item Type: | Article |
---|---|

Keywords: | Average run length; EWMA X chart; Percentiles of the run-length distribution; Run sum X chart; Standard deviation of the run length |

Journal: | Journal of Quality Measurement and Analysis |

ID Code: | 10200 |

Deposited By: | ms aida - |

Deposited On: | 07 Mar 2017 04:11 |

Last Modified: | 15 Mar 2017 07:08 |

Repository Staff Only: item control page