A control plan is a written summary that describes what is needed to keep an improved process at its current level. This includes human resources and training requirements, actions that should be taken if measures are outside the specified range, and reactions needed to ensure process owners sustain the gains of process improvements.
The purpose of the control plan is to ensure that performance improvements made by the project team are sustained over time. The plan is created during the improve phase of the define, measure, analyze, improve, control (DMAIC) approach or a similar phase of other methodologies.
The project team should create the control plan along with the process owner and representation from all areas involved in the process. As the process changes or process knowledge increases and as measurement systems and implementation methods are evaluated and improved, the plan should be updated.