The test results indicate points that are beyond the control limits. A failed point indicates that a nonrandom pattern exists in the data that may be the result of special-cause variation. You should investigate these points.

·    When a point fails a test, Minitab reports it in the Session window and marks it on the Moving Average 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.

For the plastics data, the test results indicate that subgroup 28 is beyond the control limits. Investigate why this point is out of control.