On the robustness of x-charts |
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Authors: | BF Arnold E v Collani |
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Institution: | Fachbereieh Informatik/Mathematik , Lothstr, D - 8000, Munchen |
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Abstract: | In process control the simple x-charts are widely used. In determining an optimum economic design for such a control procedure the time of satisfactory production is usually assumed to be exponentially distributed. In this paper deviations from this optimistic approach are investigated by comparing E-optimal x-charts (using the assumption of an exponentially distributed lifetime) and M-optimal x-charts which are obtained by tfie pessimistic muumax principle applied to all possible lifetime distributions with the same mean value. The comparison shows that the differences between E- and M-optimal x-charts are only minor with respect to a suitable loss function and therefore, the model under consideration is verv robust against deviations from the assumption about the distribution of the time of satisfactory production. |
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Keywords: | Quality control process control A X-harts economic design robustness exponential distribution minimax principle |
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