• 품질경영학회지
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• 제22권1호
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• pp.82-95
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• 1994

When independent individual measurements are taken both $S/c_4$ and $\bar{R}/d_2$ are unbiased estimators of the process standard deviation. However, with dependent data $\bar{R}/d_2$ is not an unbiased estimator of the process standard deviation. On the other hand $S/c_4$ is an asymptotic unbiased estimator. If there exists correlation in the data, positive(negative) correlation tends to increase(decrease) the ARL. The effect of using $\bar{R}/d_2$ is greater than $S/c_4$ if the assumption of independence is invalid. Supplementary runs rule shortens the ARL of X control charts dramatically in the presence of correlation in the data.

• 대한산업공학회지
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• 제34권3호
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• pp.328-336
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• 2008

This research proposes a method for economic-statistical design of adaptive moving average (A-MA) charts. The basic idea of the A-MA chart is to accumulate previous samples selectively in order to increase the sensitivity. The A-MA chart is a kind of adaptive chart such as the variable sampling size (VSS) chart. A major advantage of the A-MA chart over the VSS chart is that it is easy to maintain rational subgroups by using the fixed sampling size. A steady state cost rate function is constructed based on Lorenzen and Vance (1986) model. The cost rate function is optimized with respect to five design parameters. Computational experiments show that the A-MA chart is superior to the VSS chart as well as to the Shewhart $\bar{X}$ chart in the economic-statistical sense.

• Journal of the Korean Data and Information Science Society
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• 제14권4호
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• pp.939-950
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• 2003

Control charts are very useful tool for monitoring of process characteristics. This paper discusses the problem of design of control limits when the subgroups are composed by cluster sampling type. As an alternative method of design of control limits XbBar chart is proposed, which uses the control limits based on the variation between subgroups instead of using classical variation within subgroups. Two examples are presented for reasonable design of control limits and conditions of subgroups based on the cluster sampling. Through examples the guidelines for making proper control limits are proposed.

• 산업공학
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• 제6권1호
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• pp.19-30
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• 1993

Various types of control charts are available, but their full advantages are not being utilized due to the lack of experts who can select, design, implement, and interpret. An expert system is developed which would perform these functions as if each process had a resident expert.

• Journal of the Korean Data and Information Science Society
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• 제11권2호
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• pp.217-223
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• 2000

In this paper, we develop optimal decision interval exponentially weighted moving average(EWMA) scheme for the process mean and the reciprocal measure of dispersion of the inverse Gaussian distribution.

• International Journal of Quality Innovation
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• 제1권1호
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• pp.81-88
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• 2000

• 품질경영학회지
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• 제26권3호
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• pp.31-45
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• 1998

This paper proposes a method of designing one-sided cumulative scored control charts to control the process mean with a normally distributed quality characteristic. The average run length(ARL) is obtained from the average sample number of sequential probability ratio test(SPRT) on trinomial distribution. Using the analogy between cumulative scored control chart and SPRT for trinomial observations, a procedure is presented to determine three control chart parameters; lower and u, pp.r scoring boundaries and action limit. The parameters are determined by minimizing the ARL when the process is out of control with prespecified ARL when the process is in control.

• Journal of the Korean Data and Information Science Society
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• 제26권1호
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• pp.261-269
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• 2015

Nowadays the application of change point analysis has been indispensable in a wide range of areas such as quality control, finance, environmetrics, medicine, geographics, and engineering. Identification of times where process changes would help minimize the consequences that might happen afterwards. The main objective of this paper is to compare the change-point detection capabilities of Bayesian estimate and maximum likelihood estimate. We applied Bayesian and maximum likelihood techniques to formulate change points having a step change and multiple number of change points in a Poisson rate. After a signal from c-chart and Poisson cumulative sum control charts have been detected, Monte Carlo simulation has been applied to investigate the performance of Bayesian and maximum likelihood estimation. Change point detection capacities of Bayesian and maximum likelihood estimation techniques have been investigated through simulation. It has been found that the Bayesian estimates outperforms standard control charts well specially when there exists a small to medium size of step change. Moreover, it performs convincingly well in comparison with the maximum like-lihood estimator and remains good choice specially in confidence interval statistical inference.

• 한국전자거래학회지
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• 제25권1호
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• pp.83-107
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• 2020

데이터의 성격과 시각화의 목적에 따라 비즈니스 차트를 선택하는 것은 비즈니스 분석에 유용한 지식이다. 그러나 현재 시각화 도구에는 상황에 맞는 비즈니스 차트를 선택할 수 있는 기능이 부족하다. 또한 매번마다 시각화 방법에 대해 전문가의 도움을 요청하는 것은 비용과 시간이 소요된다. 따라서 본 연구의 목적은 온라인으로 게시된 문서로부터 비즈니스 차트 선정 규칙에 대한 지식을 추출하여 비즈니스 차트 생산성을 향상시키는 방법을 제안하는 것이다. 이를 위해 인터넷에서 비즈니스 차트를 묘사하는 한국어, 영어 및 중국어 비정형 데이터를 수집하고 TF-IDF를 사용하여 컨텍스트와 비즈니스 차트 간의 관계를 계산했다. 또한 Galois 래티스를 사용하여 비즈니스 차트 선택 규칙을 생성했다. 제안된 방법으로 생성된 규칙의 품질을 평가하기 위해 실험군과 대조군에 대해 실험을 수행했다. 그 결과 제안된 방법으로 의미 있는 규칙이 추출되었음을 확인했다. 본 연구의 결과물로 시각화 전문가의 도움 없이도 사무직 직원들이 비즈니스 차트를 효율적으로 선택할 수 있을 것으로 기대된다. 또한 작업 중인 문서를 기반으로 비즈니스 차트를 추천함으로 직원 교육에 유용할 것이다.

• International Journal of Quality Innovation
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• 제5권1호
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• pp.52-67
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• 2004

Successful implementation of statistical process control techniques requires for operational definitions and precise measurements. Nevertheless, very often analysts can dispose of process data available only by linguistic terms, that would be a waste to neglect just because of their intrinsic vagueness. Thus a hybrid approach, which integrates fuzzy set theory and common statistical tools, sounds useful in order to improve effectiveness of statistical process control in such a case. In this work, a fuzzy approach is adopted to manage linguistic information, and the use of a Chi-squared control chart is proposed to monitor process performance.