GP 4.2 Stabilize Subprocess Performance
The purpose of this generic practice is to stabilize the performance of one or more sub-processes of the defined (capability level 3) process that are critical contributors to the overall performance using appropriate statistical and other quantitative techniques. Stabilizing selected sub-processes of the process supports predicting the ability of the process to achieve the established quantitative quality and process performance objectives.

A stable sub-process shows no significant indication of special causes of process variation. Stable sub-processes are predictable within the limits established by the natural bounds of the sub-process. Variations in the stable sub-process are due to a constant system of chance causes, and the magnitude of the variations may be small or large.

Predicting the ability of the process to achieve the established quantitative objectives requires a quantitative understanding of the contributions of the sub-processes that are critical to achieving these objectives and establishing and managing against interim quantitative objectives over time.

Selected process and product measures are incorporated into the measurement repository to support process performance analysis and future fact-based decision making.