New Memory-Type Control Charts for Monitoring Process Mean and Dispersion

Ajadi, Jimoh Olawale; Riaz, Muhammad

doi:10.24200/sci.2017.4483

Scientia Iranica

2017

DOI: 10.24200/sci.2017.4483

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New Memory-Type Control Charts for Monitoring Process Mean and Dispersion

Jimoh Olawale Ajadi

Muhammad Riaz

Abstract: Abstract. Control chart is widely used to monitor the quality of products of industrial or business processes. Max-CUSUM and Max-EWMA are based on memory-type control charts that monitor the process mean and standard deviation simultaneously. This article introduces four new control charts that monitor the process mean and dispersion simultaneously. The proposed control charting schemes are compared with the existing counterparts including Max-EWMA, Max-CUSUM, SS-EWMA, and SS-CUSUM. A case study is presented f… Show more

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Cited by 2 publications

References 15 publications

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An Efficient Mixed-Memory-Type Control Chart for Normal and Non-Normal Processes

et al. 2019

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Statistical process control techniques are commonly used to monitor process performance. Control charting technique is the most sophisticated tool of SPC and is categorized as memoryless and memory-type control charts. Shewhart-type control charts have low efficiency in detecting the small changes in the process parameters and named as memory-less control charts, and memory-type control charts (for example cumulative sum (CUSUM) and exponentially weighted moving average (EWMA) charts) are very sensitive to small persistent shifts. In connection with enhancing the performance of CUSUM and EWMA charts, an efficient variant of memory-type charts for the location parameter is developed based on mixing the double exponentially weighted moving average (DEWMA) chart and CUSUM chart by performing exponential smoothing twice. Performance of the proposed efficient variant is compared with existing counterparts under normal and non-normal (heavy tails and skewed) environments. The study also provides an industrial application related to the monitoring of weights of quarters made by mint machine placed into service at U.S. Mint. From theoretical and numerical studies, it is revealed that proposed variant of memory-type charts outperforms the counterparts in detecting shifts of small and moderate magnitude.

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An Efficient Mixed-Memory-Type Control Chart for Normal and Non-Normal Processes

et al. 2019

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On the Performance of Median Based Tukey and Tukey-EWMA Charts Under Rational Subgrouping

et al. 2019

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Control chart (CC) is used to monitor the special causes that arise during the process monitoring.These special causes produce continual shifts in the process parameters that last until it is identified and removed. There is a need for such techniques, which present the true representation of the entire process. Rational subgrouping is an essential concept in Statistical Process Control (SPC) which is seldom overlooked by the practitioner. Hence, most of the manufacturing, engineering, and production processes give output products in the form of batches over smaller intervals of time. The aim of this study is to provide a median based design for Tukey and Tukey-EWMA control charts under subgrouping. It will use the idea of boxplot to monitor the process behavior. This study also provides a brief discussion regarding selecting and forming subgroups from the process data. The performance of the median based Tukey and Tukey-EWMA charts are judged using Average, Median and Standard-Deviation run-length as performance measures. We have considered subgroup sizes of m=1,5 &10 at pre-specified ARL0 equal to 370. To real-life applications of the median based tukey designs are also presented to show their implementation in food manufacturing and hard-bake processes.2

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New Memory-Type Control Charts for Monitoring Process Mean and Dispersion

Cited by 2 publications

References 15 publications

An Efficient Mixed-Memory-Type Control Chart for Normal and Non-Normal Processes

An Efficient Mixed-Memory-Type Control Chart for Normal and Non-Normal Processes

On the Performance of Median Based Tukey and Tukey-EWMA Charts Under Rational Subgrouping

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