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Change-point estimation of the process fraction non-conforming with a linear trend in statistical process control

Zandi, F ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1080/0951192X.2011.608720
  3. Abstract:
  4. Despite the fact that control charts are able to trigger a signal when a process has changed, it does not indicate when the process change has begun. The time difference between the changing point and a signal of a control chart could cause confusions on the sources of the problems. Knowing the exact time of a process change would help to reduce the time for identification of the special cause. In this article, a model for the change-point problem is first introduced and a maximum-likelihood estimator (MLE) is applied when a linear trend disturbance is present. Then, Monte Carlo simulation is applied in order to evaluate the accuracy and the precision performances of the proposed change-point estimator. Next, the proposed estimator is compared with the MLE of the process fraction non-conforming change point derived under simple step and monotonic changes following signals from a Shewhart np control chart. The results show that the MLE of the process change point designed for the linear trend outperforms the MLE designed for step and monotonic changes when a linear trend disturbance is present
  5. Keywords:
  6. Change point ; Maximum-likelihood estimation ; np charts ; Process fraction non-conforming ; Change-points ; Fraction non-conforming ; Process Improvement ; Statistical process ; Computer simulation ; Estimation ; Flowcharting ; Maximum likelihood estimation ; Monte Carlo methods ; Statistical process control
  7. Source: International Journal of Computer Integrated Manufacturing ; Volume 24, Issue 10 , 2011 , Pages 939-947 ; 0951192X (ISSN)
  8. URL: http://www.tandfonline.com/doi/abs/10.1080/0951192X.2011.608720