An x chart based on standard deviations (instead of ranges) is made by plotting sample means with a centerline at x and control limits at x + A3s and x A3s, where A3 is found in Table 14-2 and s is the mean of the sample standard deviations. Use the data in Table 14-1 to construct an x chart based on standard deviations. Compare the result to the x chart based on sample ranges (as in Example 5).