A run of 8 or more consecutively plotted points occurring on one side of the mean is a sign that a shift or trend in the process has begun.

UCL = Upper Control Limit
LCL = Lower Control Limit
x-double bar = Mean (average of all the x-bar values (subgroup averages))

Note: A plot on the process mean is included in the run.

Runs can indicate a step change in the process, resulting from, for example:

A run below the mean indicates an improvement on Range, Standard Deviation, and Attribute charts.