Hybrid exponentially weighted moving average control chart for mean by using different ranked set sampling schemes.

In this paper, different schemes of ranked set sampling (RSS) are used to design a new hybrid exponentially weighted moving average (HEWMA) control chart having more sensitivity to small and moderate shifts. The average run length and standard deviation of run length based on Monte-Carlo simulations are used as an evaluation measure for the sensitivity of the proposed control chart. They indicate that the HEWMA using RSS schemes significantly increases the performance of the control chart. In addition, the suggested control chart dominates classical exponentially weighted moving average control charts (EWMA), EWMA based on RSS, and HEWMA control charts using simple random sampling in detecting the small/moderate shifts in the process mean. An example containing real data is also given to further explain the application. [ABSTRACT FROM AUTHOR]