• Title/Summary/Keyword: Statistical Control Chart

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Development of Fuzzy-Statistical Control Chart for Processing Uncertain Process Information (불명확한 공정정보 처리를 위한 퍼지-통계적 관리도의 개발)

  • 김경환;하성도
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.2
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    • pp.75-80
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    • 1998
  • Process information is known to have the continuous distribution in many manufacturing processes. Generalized p-chart has been developed for controlling processes by classifying the information characteristics into several groups. But it is improper to describe continuous processes with the classified process informal ion, which is based on the classical set concept. Fuzzy control chart, has been developed for the control of linguistic data, but it is also based on the dichotomous notion of classical set theory. In this paper, fuzzy sampling method is studied in order to process the uncertain data properly. The method is incorporated with the fuzzy control chart. Statistical characteristics of the fuzzy representative value are utilized to device the fuzzy-statistical control chart. The fuzzy-statistical control chart is compared with the generalized p-chart and both the sensitivity to the process information distribution change pared robustiness against the noise on the process information of the fuzzy-statistical control chart are shown to be superior.

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A Comparison of the performance of mean, median, and precedence control charts for nonnormal data

  • Kim, Jung-Hee;Lee, Sung-Im;Park, Heon-Jin;Lee, Jae-Cheol;Jang, Young-Chul
    • Proceedings of the Korean Statistical Society Conference
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    • 2005.05a
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    • pp.197-201
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    • 2005
  • In this article, we will compare the performance of the mean control chart, the median control chart, the transformed mean control chart, the transformed median control chart, and the precedence control chart by simulation study. For control charts with transformed data, Yeo-Johnson transformation is used. Under the in-control condition, ARL's in all control charts coincide with the designed ARL in the normal distribution, but in the other distributions, only the precedence control chart provides the in-control ARL as designed. Under the out-of-control condition, the mean control chart is preferred in the normal distribution and the median control chart is preferred in the heavy-tailed distribution and the precedence control chart outperforms in the short-tailed distribution.

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Development of VSI Synthetic Control Chart (가변샘플링기법을 이용한 합성관리도의 개발)

  • Song, Suh-Ill;Park, Hyun-Kyu
    • Journal of Korean Society for Quality Management
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    • v.33 no.1
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    • pp.1-10
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    • 2005
  • This paper develops a new VSI $\={X}-CRL$ synthetic control chart that considers convenience of use in the field, and perception of change of process applying VSI techniques to synthetic control chart, simultaneously. We found the optimal sampling interval and various control limit factor of the suggested chart using markov chain. Comparison and analysis is carried out between synthetic VSI $\={X}-CRL$ chart and other chart in the statistical aspect; $\={X}$ control chart, VSI $\={X}$ chart, another synthetic chart. In case that the process follows normal distribution, the proposed VSI $\={X}-CRL$ synthetic control chart in detecting process mean shift showed the best performance in aspect of statistical performance, regardless of control limit L of CRL/S control chart.

A Statistical Control Chart for Process with Correlated Subgroups

  • Lee, Kwang-Ho
    • Communications for Statistical Applications and Methods
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    • v.5 no.2
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    • pp.373-381
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    • 1998
  • In this paper a new control chart which accounts for correlation between process subgroups will be proposed. We consider the case where the process fluctuations are autocorrelated by a stationary AR(1) time series and where n($\geq1$) items are sampled from the process at each sampling time. A simulation study is presented and shows that for correlated subgroups, the proposed control chart makes a significant improvement over the traditionally employed X-bar chart which ignores subgroup correlations. Finally, we illustrate the proposed chart by comparing the standardized residuals and X-bar chart on a data set of motor shaft diameters.

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A VSSI-CRL Synthetic Control Chart (VSSI-CRL 합성관리도)

  • Lee Jae-Won;Lim Tae-Jin
    • Journal of the Korean Operations Research and Management Science Society
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    • v.30 no.4
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    • pp.1-14
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    • 2005
  • We propose a VSSI-CRL(Variable Sampling Size and Samplina Interval-Conforming Run length) synthetic control chart in order to improve the statistical characteristics of both the VSSI chart and the CRL synthetic chart. The VSSI-CRL chart utilizes VSSI sampling scheme, but it produces a signal only when the CRI is less than a given limit. An algorithm for calculating the ARL(Average Run length) and ATS(Average Time to Signal) of the VSSI-CRL chart is developed by employing Markov chain method. We present some lemmas for describing the statistical characteristics of the VSSI-CRL chart under in-control state. A procedure for designing the VSSI-CRL chart is proposed based on the lemmas. Extensive comparative studios show that the VSSI-CRL chart is superior to the CRL synthetic chart or the VSSI chart in general, and is comparable to the EWMA chart in ATS performance.

Economic-Statistical Design of Adaptive Moving Average (A-MA) Control Charts (적응형 이동평균(A-MA) 관리도의 경제적-통계적 설계)

  • Lim, Tae-Jin
    • Journal of Korean Institute of Industrial Engineers
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    • v.34 no.3
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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.

An Economic-Statistical Design of Moving Average Control Charts

  • Yu, Fong-Jung;Chin, Hsiang;Huang, Hsiao Wei
    • International Journal of Quality Innovation
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    • v.7 no.3
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    • pp.107-115
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    • 2006
  • Control charts are important tools of statistical quality control. In 1956, Duncan first proposed the economic design of $\bar{x}-control$ charts to control normal process means and insure that the economic design control chart actually has a lower cost, compared with a Shewhart control chart. An moving average (MA) control chart is more effective than a Shewhart control chart in detecting small process shifts and is considered by some to be simpler to implement than the CUSUM. An economic design of MA control chart has also been proposed in 2005. The weaknesses to only the economic design are poor statistics because it dose not consider type I or type II errors and average time to signal when selecting design parameters for control chart. This paper provides a construction of an economic-statistical model to determine the optimal parameters of an MA control chart to improve economic design. A numerical example is employed to demonstrate the model's working and its sensitivity analysis is also provided.

A Note on the Median Control Chart

  • Park, Hyo-Il
    • Communications for Statistical Applications and Methods
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    • v.20 no.2
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    • pp.107-113
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    • 2013
  • This study reviews several well-known control charts for the location parameter with a discussion of the relationship between the maintenance of the control chart and a series of hypotheses testing. As a by-product, we then propose a new median control chart with the sign test statistic. We also modify the nonparametric control charts to easily understand the relation. Then we illustrate the construction of several median control charts with the industrial data and compare the efficiency among several control charts. Finally, we discuss some interesting features for the median control charts as concluding remarks.

Statistical Efficiency of VSSI $\bar{X}$ Control Charts for the Process with Two Assignable Causes (두 개의 이상원인이 존재하는 공정에 대한 VSSI $\bar{X}$ 관리도의 통계적 효율성)

  • Lee Ho-Jung;Lim Tae-Jin
    • Journal of Korean Society for Quality Management
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    • v.32 no.4
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    • pp.156-168
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    • 2004
  • This research investigates the statistical efficiency of variable sampling size & sampling interval(VSSI) $\bar{X}$ charts under two assignable causes. Algorithms for calculating the average run length(ARL) and average time to signal(ATS) of the VSSI $\bar{X}$ chart are proposed by employing Markov chain method. States of the process are defined according to the process characteristics after the occurrence of an assignable cause. Transition probabilities are carefully derived from the state definition. Statistical properties of the proposed chart are also investigated. A simple procedure for designing the proposed chart is presented based on the properties. Extensive sensitivity analyses show that the VSSI $\bar{X}$ chart is superior to the VSS or VSI $\bar{X}$ chart as well as to the Shewhart $\bar{X}$ chart in statistical sense, even tinder two assignable causes.

Overview of Operations Strategy for Service Layout and Statistical Process Control (서비스 배치 및 SPC 운영 전략)

  • Choi, Sung-Woon
    • Journal of the Korea Safety Management & Science
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    • v.8 no.6
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    • pp.109-118
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    • 2006
  • This paper proposes service layout strategy considering service characteristics by the use of benchmarking production system such as layout by P-Q chart, improvement tool, automated system, Toyota production system and lean production system. This paper represents operation methodology of statistical process control using control chart for service performance outcomes.