• The usual CUSUM chart for the mean (CUSUM-X̄) is a chart used to quickly detect small to moderate shifts in a process. In presence of outliers, this chart is known to be more robust than other mean-based alternatives like the Shewhart mean chart but it is nevertheless affected by these unusual observations because the mean (X̄) itself is affected by the outliers. An outliers robust alternative ...

This study develops a least squares support vector machines (LS-SVM) based model for bivariate process to diagnose abnormal patterns of process mean vector, and to help identify abnormal variable(s) when Shewhart-type multivariate control charts based on Hotelling’s T 2 are used. On the basis of studying and defining the normal/abnormal patterns of the bivariate process mean shifts, a LS-SVM pa...

Since the seminal contribution by Shewhart, the dominating approach to production is to minimize all variation in order to get the productive activities into control. Thus, the goal is to avoid all such complexity and uncertainty which could disturb this tight control. This approach is applied in lean production, which is considered to be the superior production template of today. It has to be ...

The presence of dispersion/variability in any process is understood and its careful monitoring may furnish the performance of any process. The interquartile range (IQR) is one of the dispersion measures based on lower and upper quartiles. For efficient monitoring of process dispersion, we have proposed auxiliary information based Shewhart-type IQR control charts (namely IQRr and IQRp charts) ba...

Despite the fact that control charts are able to trigger a signal when a process has changed, it does not indicate when the process change has begun. The time difference between the changing point and a signal of a control chart could cause confusions on the sources of the problems. Knowing the exact time of a process change would help to reduce the time for identification of the special cause....

Overcrowding in emergency departments (EDs) is a primary concern for hospital administration. They aim to efficiently manage patient demands and reducing stress the ED. Detection of abnormal ED (patient flows) systems aids managers obtain appropriate decisions by optimally allocating available resources following attendance. This paper presents monitoring strategy that provides an early alert w...

The influence of the estimation of parameters in Shewhart control charts is investigated. It is shown by simulation and asymptotics that (very) large sample sizes are needed to accurately determine control charts if estimators are plugged in. Correction terms are developed to get accurate control limits for common sample sizes in the in-control situation. Simulation and theory show that the new...

Water in pharmaceutical industry is a key ingredient in many industrial processes, including machine washing and preparation of most medicinal products. The process of regular monitoring for the microbiological quality of water at the points of use is a critical aspect in ensuring the compliance to the limit. However, the full value of the microbiological control could be accomplished by the us...

Statistical experimentation IS the key to make the process robust to environmental noises, to produce the products ~t a lower cost and to enhance the productivity. Analysis of means and dispersions are rational extensions of the Shewhart control chart for comparing products from different design configurations in off-line quality improvement. In this article, we utilize these graphical procedur...

This paper presents an on-line Statistical Process Control (SPC) technique, based on a Generalized Likelihood Ratio Test (GLRT), for detecting and estimating mean shifts in autocorrelated processes that follow a normally distributed Autoregressive Integrated Moving Average (ARIMA) model. The GLRT is applied to the uncorrelated residuals of the appropriate time-series model. The performance of t...