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Journal of Korean Society for Quality Management 1987;15(2): 10-. |
| 비정규분포공정(非正規分布工程)에서 메디안특수관리도(特殊管理圖)의 모형설계(模型設計) |
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| 아주대학교 공대 산업공학과 |
| Design of Median Control Chart for Nonnormally Distributed Processes |
| Yong-Baek Sin |
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| ABSTRACT |
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Statistical control charts are useful tools to monitor and control the manufacturing processes and are widely used in most Korean industries. Many Korean companies, however, do not always obtain desired results from the traditional control charts by Shewhart such as the $overline{X}$-chart, X-chart, $widetilde{X}$-chart, etc. This is partly because the quality charterstics of the process are not distributed normally but are skewed due to the intermittent production, small lot size, etc. In the Shewhart $overline{X}$-chart, which is the most widely used one in Korea, such skewed distributions make the plots to be inclined below or above the central line or outside the control limits although no assignable causes can be found. To overcome such shortcomings in nonnormally distributed processes, a distribution-free type of confidence interval can be used, which should be based on order statistics. This thesis is concerned with the design of control chart based on a sample median which is easy to use in practical situation and therefore properties for nonnormal distributions may be easily analyzed. Control limits and central lines are given for the more famous nonnormal distributions, such as Gamma, Beta, Lognormal, Weibull, Pareto, and Truncated-normal distributions. |
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