Adaptive RR charts with variable parameters

The Shewhart RR control chart (RR chart) has been widely used to monitor process variance. However, the main disadvantage of an RR chart is its slowness to signal small increases on the variability. In this paper, ideas of adaptive control charts are extended to the Shewhart RR chart for improving efficiency in signaling increases on the variance. A Markov chain model is applied to evaluate its performance. The statistical performance shows that the RR chart with variable parameters (VP) is more sensitive to variance increases.