A Note on the Factor Values of Three Common Shewhart Variables Control Charts

It is a common practice that people directly use the published factor values in constructing Shewhart variables control charts. Currently, the values of most of the factors are published typically with up to 4 decimal places of precision and from sample size n = 2 through 25; a number of discrepancies in the published factor values from different sources also exist. In this paper, we compute and provide the factor values with more precision of 10 decimal places and consecutively through n = 100 for three commonly used variables control charts: xbar-R charts, xbar-s charts, and XmR charts