An x̅̅ chart based on standard deviations (instead of ranges) is constructed by plotting sample means with a centerline at x̅̅ and control limits at x̅̅ + A₃x̅ and x̅̅ - A₃x̅, where A₃ is found in Table 14-2 on page 660 and x̅ is the mean of the sample standard deviations. Use the data in Table 14-1 on page 655 to construct an x̅̅ chart based on standard deviations. Compare the result to the x̅̅ chart based on sample ranges in Example 5 “x̅ Chart of Altimeter Errors.”

Table 14-1:

Table 14-2: