Economic design of EWMA control charts based on loss function

Date

2009

Authors

Serel, D. A.

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Source Title

Mathematical and Computer Modelling

Print ISSN

0895-7177

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Publisher

Elsevier

Volume

49

Issue

3-4

Pages

745 - 759

Language

English

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Abstract

For monitoring the stability of a process, various control charts based on exponentially weighted moving average (EWMA) statistics have been proposed in the literature. We study the economic design of EWMA-based mean and dispersion charts when a linear, quadratic, or exponential loss function is used for computing the costs arising from poor quality. The chart parameters (sample size, sampling interval, control limits and smoothing constant) minimizing the overall cost of the control scheme are determined via computational methods. Using numerical examples, we compare the performances of the EWMA charts with Shewhart over(X, -) and S charts, and investigate the sensitivity of the chart parameters to changes in process parameters and loss functions. Numerical results imply that rather than sample size or control limits, the users need to adjust the sampling interval in response to changes in the cost of poor quality.

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