Control chart pattern recognition using average of cumulative sum

Abstract

The statistical process control chart is a monitoring technique useful in determining whether a process is behaving as intended or if there are some unnatural causes of variation. A process is considered to be out of control if a point falls outside the control limits or a series of points exhibit an unnatural pattern (also known as nonrandom variation). Analysis of unnatural patterns is an important aspect of control charting. It is well known that a particular unnatural pattern on a control chart is often associated with a specific set of assignable causes. Identification of unnatural patterns can greatly narrow the set of possible causes that must be investigated, hence facilitating the rapid diagnosis and corrective action.