A practical example of common cause and special cause variation aids in the understanding of control charts.
Control charts are used to monitor processes and ensure the processes are in control, but all processes are subject to degrees of variation. Most of the variation is inherent in the process and the surrounding environment and is referred to as common cause variation. Variations not normal to the process are referred to as special cause variation. To better understand special and common cause variation, they are applied to an everyday occurrence.