This research investigates the performance of adaptive Exponentially Weighted Moving Averages (EWMA) control charts when monitoring the standard deviation of a process. It is known that when we use a fixed value for the smoothing parameter λ of the EWMA chart we restrict its ability to detect shifts of changing magnitudes. In this paper, we propose nine EWMA charts for the standard deviation...
In this work, we study the behavior of nonparametric Shewhart-type control charts, which employ order statistics and multiple runs-type rules. The proposed class of monitoring schemes include some existing control charts. In addition, new distribution-free monitoring schemes that pertain to the class, are set up and examined extensively. Explicit expressions for determining the variability and...
The focus on every experimental process is observing, studying and understanding phenomena, which are of multivariate nature. The rapid growth of computational power, in combination with the existence of different statistical packages, has facilitated the data collection and led to the development of statistical techniques for monitoring and surveillance. In real world settings, the...