Abdu  Atta, Majed  Shoraim, Sharipah  Yahya, Ali  Abuzaid, Esam  Mahdi, 
    Enhancing R Control Chart Performance in Monitoring Process Dispersion using
Scaled Weighted Variance Method for Skewed Populations,
    Journal of Engineering and Applied Sciences,
    Volume 15,Issue 6,
    2020,
    Pages 1508-1514,
    ISSN 1816-949x,
    jeasci.2020.1508.1514,
    (https://makhillpublications.co/view-article.php?doi=jeasci.2020.1508.1514)
    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.
    Keywords: R control chart;skewed population;scaled weighted variance method;SWV-R;WV-R;SC-R