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为了提高控制图的监控效率,本文研究非正态分布下,EWMA控制图的可变样本容量设计问题。首先利用Burr分布近似各种非正态分布,构造可变样本容量的非正态EWMA控制图;其次运用马尓科夫链法计算可变样本容量非正态EWMA控制图的平均运行长度;然后与传统的非正态EWMA控制图进行比较得出:当过程中出现小波动时,可变样本容量的非正态EWMA控制图能够更快地发现过程中的异常波动,具有较小的平均运行长度,其监控效率明显优于传统的非正态EWMA控制图。 相似文献
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非参数质量控制图——中位值图 总被引:1,自引:0,他引:1
质量控制图在制造工业中有广泛的应用 .传统的控制图是在正态总体的基础上制定的 . Janacek和Meikle(1 997)利用参考样本的观念制定的中位值控制图可应用于任何总体分布 .他们制定的中位值图保持传统控制图的形式 ,且有适度的功效 ,应用方便 .本文首先介绍这种控制图的制定方法 ,然后研究它的统计效率 ,并同传统的平均值图作比较 相似文献
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The Pareto distribution plays an important role in various areas of researchIn this paper, the average run length(ARL) unbiased control charts, which monitor the shape and threshold parameters of the Pareto distribution respectively, are proposed when the incontrol parameters are knownThe effects of parameter estimation on the performance of the proposed control charts are also studiedResults show that the control charts with the estimated parameters are not suitable to be used in the known parameter case, thus the ARL-unbiased control charts for the shape and threshold parameters with the desired ARL0, which consider the variability of the parameter estimates, are further developedThe performance of the proposed control charts is investigated in terms of the ARLFinally, an example is given to illustrate the proposed control charts. 相似文献
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由于自相关过程违背了过程输出数据独立性的假定,使得传统休哈特图的有效性受到质疑。本文首先讨论控制图设计基本思想,然后分析了对自相关过程监控的残差控制图原理;进而以平均链长和各链点检出概率为准则,系统研究了AR(1)过程残差控制图的检测能力,并与休图进行了比较。最后,通过一个模拟验证了该方法的有效性。 相似文献
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用于检测生产过程的多数传统控制图都假定过程的受控分布是已知的,并假定数据服从正态分布。然而在很多情况下,由于没有足够的数据来估计过程的分布,这种假定就变得不现实,而非参数控制图却不需要任何关于分布的特殊形式的假定。另外,多数的已有控制图都是使用两个单独的均值与方差控制图来同时检测生产过程.本文中,我们提出一个新的基于Cramer-von-Mises(CvM)检验的非参数累积和控制图(称为CvM图)来同时检测过程位置参数和尺度参数。文中给出了基于不同受控平均运行长度(ARL)下的CvM图的控制限,通过步长的均值、方差及分位数来研究控制图的性能表现。最后用一个实例来说明CvM图的实际应用。 相似文献
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Distribution‐free (nonparametric) control charts are helpful in applications where we do not have enough information about the underlying distribution. The Shewhart precedence charts is a class of Phase I nonparametric charts for location. One of these charts, called the median precedence chart (Med chart hereafter), uses the median of the test sample as the charting statistic, whereas another chart, called the minimum precedence chart (Min chart hereafter), uses the minimum. In this paper, we first study the comparative performance of the Min and the Med charts, respectively, in terms of their in‐control and out‐of‐control run‐length properties in an extensive simulation study. It is seen that neither chart is best as each has its strength in certain situations. Next, we consider enhancing their performance by adding some supplementary runs‐rules. It is seen that the new charts present very attractive run‐length properties, that is, they outperform their competitors in many situations. A summary and some concluding remarks are given. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Nonparametric control charts have received increasing attention in process monitoring. In this article, a new nonparametric sign (SN) control chart with variable sample size (VSS) for a finite horizon process is developed. The novelty of this research lies in the incorporation of the VSS technique into the nonparametric SN chart for a finite horizon process, hence, resulting in the development of a more sensitive nonparametric short run chart. The statistical performance of the new nonparametric VSS SN control chart is evaluated and compared with the existing fixed sample size (FSS) SN chart for a finite horizon process. The charts' performances are compared using the truncated average run length (TARL) and truncated standard deviation of the run length (TSDRL) criteria. The results obtained show that the nonparametric VSS SN short run chart is always quicker than the FSS SN short run chart in detecting process shifts for various underlying process distributions, hence, reducing scrap and rework cost. Finally, an application of the proposed control charting scheme is shown through a real-life example on the fill volume of soft drink beverage bottles. 相似文献
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自相关对常规控制图影响的模拟研究与案例分析 总被引:1,自引:0,他引:1
常规统计控制图的基本假设前提是观测值独立同分布,而在实际生产过程中,质量指标值常表现出自相关现象,违背独立性假定。本文运用平均链长(ARL)研究自相关过程为AR(1)时对常规控制图的影响,并比较了常规控制图和残差控制图对序列相关过程的控制效果。模拟结果和实例分析表明:当过程序列相关时,使用常规作图法估计出的标准差是有偏的,致使控制限设置错误和常规控制图检测能力降低。因此,在一些统计过程控制中,须考虑自相关现象并采用适当的控制图方法。 相似文献
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In recent years, statistical process control (SPC)
has been widely used to monitor the performance of clinical practitioners,
such as surgeons and general practitioners. In this paper, two risk-adjusted
geometric control charts namely cumulative sum (CUSUM) and weighted likelihood
ratio test (WLRT) are proposed to monitor surgery performance in phase II.
The performance of the proposed control charts is evaluated and compared by
simulation experiments for different shift values in the parameters of a
risk-adjusted logistic regression model in terms of the average run length
(ARL) criterion. The results show that all methods work well in the sense
that they can effectively detect shifts in the process parameters. 相似文献
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Continuous surveillance of the coefficient of variation is a quality control issue worthy of consideration in several manufacturing and service‐oriented companies. In this paper, we present a new method to monitor the squared coefficient of variation by means of two one‐sided cumulative sum‐type control charts. We study the run length properties of the proposed charts using a Markov chain approach. Several tables are given in order to show the sensitivity of the proposed charts for different deterministic shift sizes and their performance for the random shift size condition. The results show that the proposed control charts have attractive performance compared with some competing charts and are better in many cases. An illustrative example is discussed on a real dataset. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Control charts with exponentially weighted moving average (EWMA) statistics (mean and variance) are used to jointly monitor the mean and variance of a process. An EWMA cost minimization model is presented to design the joint control scheme based on pure economic or both economic and statistical performance criteria. The pure economic model is extended to the economic-statistical design by adding constraints associated with in-control and out-of-control average run lengths. The quality related production costs are calculated using Taguchi’s quadratic loss function. The optimal values of smoothing constants, sampling interval, sample size, and control chart limits are determined by using a numerical search method. The average run length of the control scheme is computed by using the Markov chain approach. Computational study indicates that optimal sample sizes decrease as the magnitudes of shifts in mean and/or variance increase, and higher values of quality loss coefficient lead to shorter sampling intervals. The sensitivity analysis results regarding the effects of various inputs on the chart parameters provide useful guidelines for designing an EWMA-based process control scheme when there exists an assignable cause generating concurrent changes in process mean and variance. 相似文献
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M. V. Koutras S. Bersimis P. E. Maravelakis 《Methodology and Computing in Applied Probability》2007,9(2):207-224
The aim of this paper is to present the basic principles and recent advances in the area of statistical process control charting
with the aid of runs rules. More specifically, we review the well known Shewhart type control charts supplemented with additional
rules based on the theory of runs and scans. The motivation for this article stems from the fact that during the last decades,
the performance improvement of the Shewhart charts by exploiting runs rules has attracted continuous research interest. Furthermore,
we briefly discuss the Markov chain approach which is the most popular technique for studying the run length distribution
of run based control charts.
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Although statistical process control (SPC) techniques have been focused mostly on detecting constant mean shifts, dynamic
and time-varying process changes frequently occur in the monitoring of feedback-controlled and autocorrelated processes. In
this research, the performances of cumulative score (Cuscore), generalized likelihood ratio test (GLRT), and cumulative sum
(CUSUM) charts in detecting a dynamic mean change that finally approaches a steady-state value are compared. Theoretical results
in average run length (ARL) comparison are provided. From the theretical study we find that, when the steady-state value is
greater or less than a critical value,Rδ/2+δ/2, the Cuscore and CUSUM charts have a different performance in detecting the mean change. We prove also that the GLRT has
the best performance among the three charts in detecting any mean change for which the steady-state value is not equal to
δ or δR, when the in-control ARL is large. 相似文献