Quality Control in Cocoa Powder Production Process: A Robust MSPC Approach
DOI:
https://doi.org/10.11113/jt.v63.1910Keywords:
Control chart, statistical process control, multivariate normal process, robust estimation, fast minimum covariance determinantAbstract
To monitor a multivariate process mean, Hotelling’s T2 control chart is often used. However, the presence of multiple outliers may go undetected due to the masking effect or swamping effect. In this study, we propose a robust Hotelling’s T2 control charts where the mean vector and the covariance matrix are estimated by using fast minimum covariance determinant (FMCD) which gives a high breakdown point estimates. This study found that the latter approach performs far better than the former in terms of the ability in detecting an out-of-control situation during the start-up stage. We present and discuss our experience in monitoring the process mean of cocoa powder production process in a Malaysian company located in Johor Bahru.
References
Ryan, T. P. 1989. Statistical Methods for Quality Improvement. New York, NY: John Wiley and Sons.
Mason, R. L. and Young, J. C. 2002. Multivariate Statistical Process Control with Industrial Applications. SIAM, Philadelphia, PA.
Johnson, R. A. and Wichern, D. W. 2002. Applied Multivariate Statistical Analysis. 5th Ed. Upper Saddle River, NJ: Prentice Hall.
Montgomery, D. C. 2005. Introduction to Statistical Quality Control. 5th Ed. New York, NY: John Wiley and Sons.
Alt, F. B. 1982. Multivariate Quality Control: State of the Art. ASQC Quality Congress Transactions. 886–893.
Jensen, W. A., Birch, J. B. and Woodall, W. H. 2005. High Breakdown Point Estimation Methods For Phase I Multivariate Control Charts, Quality and Reliability Engineering International. 23(5): 615–629.
Hadi, A. S. 1992. Identifying Multiple Outliers in Multivariate Data. Journal of Royal Statistical Society. 54(3): 761–771.
Rousseeuw, P. J. and Van Driessen, K. 1999. A Fast Algorithm for the Minimum Covariance Determinant Estimator. Technometrics. 41(3): 212–223.
Chou, Y. M., Mason, R. L. and Young, J. C. 1999. Power Comparisons for a Hotelling’s statistic, Communications in Statistics, Part B-Simulation and Computation. 28: 1031–1050.
Verboven, S. and Hubert, M. 2005. LIBRA: A MATLAB Library for Robust Analysis. Chemometrics and Intelligent Laboratory Systems. 75:127–136.
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