Economic Design of VSI Control Charts for Monitoring Over-adjusted Process

• Main Author: 柯芝穎
• Other Authors: 楊素芬
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/23064850672911188308

碩士 === 國立政治大學 === 統計研究所 === 94 === The over-adjustment means that the process is adjusted unnecessarily when a false alarm occurs. It may result in shifts in process mean and variance affecting the quality of products and have the effect of an increase in variability and cost. In this paper, the economic variable sample interval (VSI) standard and control charts are proposed to monitor effectively the mean and variance of the over-adjusted process. We use a Markov chain approach to derive the design parameters of the standard and charts by the minimum of the cost function. An example of shampoo making process is used to illustrate the application and performance of the proposed VSI standard and charts in detecting shifts in process mean and variance. Furthermore, we compare the cost and performances for the economic FSI (fixed sampling interval) and VSI control charts. Support for this research was provided in part by the National Science Council of the Republic of China, grant No. NSC 94-2118-M-004-003.