S charts assess whether the process variation is in control. The tests for special causes detect points beyond the control limits and specific patterns in the data plotted on the chart.

·    When a point fails a test, Minitab reports it in the Session window and marks it on the S chart. A failed point indicates that there is a nonrandom pattern in the data that may be the result of special-cause variation. These points should be investigated.

·    When no points are displayed under the test results, no points failed the tests for special causes.

No points failed the tests for special causes.

The canning data did not fail any of the tests for special causes. Therefore, the S chart is in control.