Authors : Abdu Atta, Majed Shoraim, Sharipah Yahya, Ali Abuzaid and Esam Mahdi
Abstract: This study improves the performance of R control chart for monitoring process dispersion of skewed populations using scaled weighted variance method. This control chart, called Scaled Weighted Variance R control chart (SWV-R) hereafter, the SWV-R control chart compared with Skewness Correction R chart (SC-R) and Weighted Variance R chart (WV-R) in terms of false alarm. In terms of probability of detection rates the proposed SWV-R chart is compared with R chart of the exact method, SC-R and WV-R control charts. The proposed SWV-R control chart reduces to the Shewhart R control chart when the underlying distribution is symmetric. An illustrative example is given to show how the proposed SWV-R control chart is constructed and works simulations study show that the proposed SWV-R control chart has the lower false alarm rates than the SC-R and WV-R control charts, when the underlying distributions are Weibull and gamma. In terms of the probability of detection rates, the proposed SWV-R control chart is closer to R control chart with the exact method than WV-R and almost the same performance as SC-R chart.
Abdu Atta, Majed Shoraim, Sharipah Yahya, Ali Abuzaid and Esam Mahdi, 2020. Enhancing R Control Chart Performance in Monitoring Process Dispersion using Scaled Weighted Variance Method for Skewed Populations. Journal of Engineering and Applied Sciences, 15: 1508-1514.