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Variable sampling interval Shewhart control charts for monitoring the multivariate coefficient of variation
Author(s) -
Nguyen Quoc Thong,
Tran Kim Phuc,
Heuchenne Henri L.,
Nguyen Thi Hien,
Nguyen Huu Du
Publication year - 2019
Publication title -
applied stochastic models in business and industry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.413
H-Index - 40
eISSN - 1526-4025
pISSN - 1524-1904
DOI - 10.1002/asmb.2472
Subject(s) - control chart , statistics , multivariate statistics , univariate , shewhart individuals control chart , sampling (signal processing) , coefficient of variation , chart , mathematics , x bar chart , variance (accounting) , interval (graph theory) , control limits , variable (mathematics) , ewma chart , computer science , process (computing) , accounting , filter (signal processing) , combinatorics , business , computer vision , operating system , mathematical analysis
In many industrial manufacturing processes, the ratio of the variance to the mean of a quantity of interest is an important characteristic to ensure the quality of the processes. This ratio is called the coefficient of variation (CV). A lot of control charts have been designed for monitoring the CV of univariate quantity in the literature. However, the CV control charts for multivariate quantity have not received much attention yet. In this paper, we investigate a variable sampling interval (VSI) Shewhart control chart for monitoring multivariate CV. The time between two consecutive samples is allowed to vary according to the previous value of the multivariate CV, which will help the chart to detect the process shifts faster. The comparison with the fixed sampling interval Shewhart chart is implemented to highlight the advantage of the VSI method. Finally, an illustrative example is demonstrated on real data.