A statistical process control (SPC) control chart is a key process management tool, providing indication if the process is predictable and consistently capable of meeting requirements.
When used in operations to monitor KPI (key process indicators), such as product dimensions on the production floor, the control chart provides real-time management of the process, with the potential to prevent out of specification as well as over-adjustment to the machine settings. The statistical control limits on the control chart provide the expected variation of the process parameter that is plotted (generally either a measured observation or the average of two or more observations): If the process is stable, the groups will plot between the statistical control limits. In this case, and only this case, the process is predictable, which is highly desirable from a process management perspective.