When the points show the same pattern of change over equal periods of time, the process is considered cyclical. Knowing and understanding the cycles of a process help in making staffing decisions. This pattern suggests that the data is grouped incorrectly. Hugging the center line does not indicate a controlled process. The data needs to be regrouped into more appropriate categories, then charted on a new control chart.
Points occur continually on one side of the center line.
A run suggests the process has undergone a permanent change and is now becoming stable. A shift occurs when the mean of the process goes up or down. A permanent change in the process has occurred. Control lines should be recomputed for future interpretation.