How to Improve Process Capability

process flow image by Christopher Hall from

Process capability is a measurement used to reflect how well a process functions within the normal limits of variability. These limits of variability are the upper and lower control limits. The goal is to have the process occur within the range of variability. When the process occurs outside the range, the process is not capable of producing a consistently high quality product or service.

Examine the process flowchart. Look for areas of duplicate work, extended cycle times or rework. If there are areas of duplication, extended cycle times or rework, work with the stakeholders to remove the unnecessary steps. Speak with stakeholders to help them understand that only those items critical to the customer receiving a quality product or service will remain.

Examine the control charts for outliers and variability. If there are outliers or large swings in variability, work to understand if the variability is due to common causes or special causes. A common cause variation is predictable and present in every process. A special cause variation is due to special or unusual circumstances.

Prioritize improvements and create new control charts to examine the effects of the changes.


  • At each change in the process, new sample data must be collected.


  • Do not introduce the changes into the process all at once. This may adversely affect the other parts of the process.



About the Author

Hunter Taylor has been a freelance writer since 2005. She has authored articles for the "The Social Contract Journal," as well as newspapers, legislative magazines and e-newsletters for state legislators and organizations. Taylor holds a Master of Business Administration from Shorter University.

Photo Credits

  • process flow image by Christopher Hall from