A Variable Sampling Interval Synthetic Xbar Chart for the Process Mean |
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| Authors: | Lei Yong Lee Michael Boon Chong Khoo Sin Yin Teh Ming Ha Lee |
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| Affiliation: | 1School of Mathematical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia;2School of Management, Universiti Sains Malaysia, 11800 Penang, Malaysia;3School of Engineering, Computing and Science, Swinburne University of Technology (Sarawak Campus), Sarawak, Malaysia;Tianjin University, CHINA |
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| Abstract: | The usual practice of using a control chart to monitor a process is to take samples from the process with fixed sampling interval (FSI). In this paper, a synthetic control chart with the variable sampling interval (VSI) feature is proposed for monitoring changes in the process mean. The VSI synthetic chart integrates the VSI chart and the VSI conforming run length (CRL) chart. The proposed VSI synthetic chart is evaluated using the average time to signal (ATS) criterion. The optimal charting parameters of the proposed chart are obtained by minimizing the out-of-control ATS for a desired shift. Comparisons between the VSI synthetic chart and the existing , synthetic , VSI and EWMA charts, in terms of ATS, are made. The ATS results show that the VSI synthetic chart outperforms the other type charts for detecting moderate and large shifts. An illustrative example is also presented to explain the application of the VSI synthetic chart. |
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