s Chart In this section we described control charts for R and x based on ranges.

Control charts for monitoring variation and center (mean) can also be based on standard deviations. An s chart for monitoring variation is constructed by plotting sample standard deviations with a centerline at s (the mean of the sample standard deviations)

and control limits at B4s and B3s, where B4 and B3 are found in Table 2 in this section.

Construct an s chart for the data of Table 1.

Compare the result to the R chart given in Example 3.