<Li> Eliminating assignable (special) sources of variation, so that the process is stable . </Li> <Li> Monitoring the ongoing production process, assisted by the use of control charts, to detect significant changes of mean or variation . </Li> <P> The data from measurements of variations at points on the process map is monitored using control charts . Control charts attempt to differentiate "assignable" ("special") sources of variation from "common" sources . "Common" sources, because they are an expected part of the process, are of much less concern to the manufacturer than "assignable" sources . Using control charts is a continuous activity, ongoing over time . </P> <P> When the process does not trigger any of the control chart "detection rules" for the control chart, it is said to be "stable". A process capability analysis may be performed on a stable process to predict the ability of the process to produce "conforming product" in the future . </P>

When is a process said to be in control