Sensitivity Analysis of Statistical Process Control Methods for Correlated Data

• Main Authors: Pi-Chi Chen, 陳筆琪
• Other Authors: Chau-Chen Torng
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/86351300677639218608

碩士 === 國立雲林科技大學 === 工業工程與管理研究所 === 83 === Traditional statistical process control charts assume that process observation are independent and identically distributed. In practice , however , autocorrelations and other systematic time-series effects frequently occur in process observations. Many research results indicate that even a small autocorrelation will have significant effects on traditional control chart . Therefore , we try to investigate the effects of correlated data to Shewhart and EWMA charts , and compare them to the independ- ent data . The purpose of this research is to provide a better understanding on the effects of correlated data to traditional control charts . Many authors have provide different methods in dealing with correlated data . However , due to different viewpoints in analysis , the practitioners still can't choose a suitable control chart . Therefore , another purpose of this research is to perform the sensitivity analysis of Shewhart , EWMA and SCC charts for correlated data . Simulation is conducted to find the relationship between the autocorrelation coefficient and average run length , in order to provide a criterion for pract- itioners on choosing suitable control charts . Results show that EWMA chart is suitable for negative correlated data compared to independent data . In detecting shift of process mean , SCC control chart is better for large shifts while EWMA control chart is better for small shifts .