X charts with variable sampling intervals
Technometrics
Adaptive CUSUM procedures with Markovian mean estimation
Computational Statistics & Data Analysis
Adaptive CUSUM control chart with variable sampling intervals
Computational Statistics & Data Analysis
An economic design of double sampling X charts for correlated data using genetic algorithms
Expert Systems with Applications: An International Journal
Computers and Industrial Engineering
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The Shewhart R control chart (R chart) has been widely used to monitor process variance. However, the main disadvantage of an R chart is its slowness to signal small increases on the variability. In this paper, ideas of adaptive control charts are extended to the Shewhart R 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 R chart with variable parameters (VP) is more sensitive to variance increases.