Double sampling |S| control chart with variable sample size and variable sampling interval |
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Authors: | Ming Ha Lee Michael B C Khoo |
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Institution: | 1. Faculty of Engineering, Computing and Science, Swinburne University of Technology Sarawak Campus, Kuching, Sarawak, Malaysia;2. School of Mathematical Sciences, Universiti Sains Malaysia, Penang, Malaysia |
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Abstract: | This study presents a control chart for monitoring shifts in the covariance matrix of a multivariate normally distributed process. This chart combines the double sampling, variable sample size and variable sampling interval features, and is called the DSVSSI |S| chart. A Markov chain approach is developed to design the DSVSSI |S| chart, by minimizing the average time to signal (ATS), for a specified shift size in the covariance matrix. The DSVSSI |S| chart has a better ATS performance compared to other existing charts. An example is given to illustrate the operation of the DSVSSI |S| chart. |
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Keywords: | Average time to signal Double sampling Sample generalized variance Variable sample size Variable sampling interval |
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