What’s A X-Bar & R Chart?
X-Bar & R Charts are Control Charts designed for tracking the average of sub-grouped continuous data. They consist of two separate charts; “X-Bar” stands for the “Average” Chart which tracks the mean of sub-groups of up to 6 data points and “R” stands for “Range” Chart which tracks the difference between the maximum and minimum values in the subgroup. These charts are not as sensitive to non-normal data as the I & MR Charts.
A classic example of an X-Bar & R Chart is to track the average cycle time to deliver packages by sampling 5 packages per day.