Premium
Charting techniques for monitoring a random shock process
Author(s) -
Chang T. C.,
Gan F. F.
Publication year - 1999
Publication title -
quality and reliability engineering international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 62
eISSN - 1099-1638
pISSN - 0748-8017
DOI - 10.1002/(sici)1099-1638(199907/08)15:4<295::aid-qre252>3.0.co;2-7
Subject(s) - chart , poisson distribution , geometric distribution , process (computing) , constant false alarm rate , control chart , computer science , mathematics , poisson process , goodness of fit , statistics , false alarm , algorithm , probability distribution , operating system
A modified geometric model is proposed for fitting data generated from a process where most of the samples are conforming and occasional samples are non‐conforming. These near‐zero‐defect processes are classified as processes subjected to random shocks. A graphical comparison of the goodness of fit of industrial process data using modified geometric and modified Poisson models is performed. The geometric model is found to provide a better fit than the Poisson model. Based on the modified geometric model, a charting scheme consisting of two charts is developed to monitor a process subjected to random shocks. A cumulative count of conforming chart is used to monitor the frequency of random shocks and a geometric chart is used to monitor the count of non‐conformities. The geometric chart performs better than the Poisson chart in terms of false alarm rate. The performance of the scheme is also evaluated. Copyright © 1999 John Wiley & Sons, Ltd.