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XBar control chart allows me to use the average range (or average standard deviation).
In cases where some subgroup ranges (or standard deviations) are of high / very high value in relation to the routine values (i.e. "outliers"), their effect is to inflate the average range and to inflate the limits on the chart.
To avoid cycling through a delete and revise approach it is sometimes better and easier to just create limits based on the median range.
Can we please include this as an option in JMP? I think it would valuable. Moreover, if we allow for the median moving range for IR charts, why not allow for the median range for XBar charts?