A free online reference for statistical process control, process capability analysis, measurement systems analysis, control chart interpretation, and other quality metrics.
For this test, look for groups of points moving up or down in succession. Count consecutive points, including horizontal runs within the run. This pattern is probably the result of a trend in one of the system resources. The chart below shows a group of seven points moving downward.
>> Analyze for special causes of variation
>> Any point lying outside the control limits
>> 7 or more points in a row above or below the centerline
>> Any nonrandom pattern