Process Capability Study: Confusion And Resolution

The provided process capability study PDF article below describes issues with traditional lean Six Sigma process capability indices reporting and what can be done to resolve the problems.

Process Capability Study: Traditional Approach

In a lean Six Sigma and other process capability study, process capability indices are to be reported.  The mathematics for this Cp, Cpk, Pp, and Ppk reporting not difficult, as the following figure illustrates:


process capability study formula


However,  determining a standard deviation to enter into an equation for a process capability study is dependent upon how data are acquired for the calculation, as the figure below indicates:


process capability study standard deviationn


Process Capability Calculations: Confusion And Resolution

It is important for organizations to build awareness of the exposures when using traditional process capability study metrics in their lean Six Sigma training and coaching. I have found that most people find it easy to visualize and interpret an estimated parts per million (ppm) rate beyond customer objectives/specifications as a reported process capability/performance index.

Because of this, I encourage organizations to consider using this metric with appropriate data transformations, in lieu of Cp, Cpk, Pp, and Ppk and other process metrics, whenever possible.

Another benefit of this approach is that there can now be a single unit of measure for both attribute and continuous data situations within manufacturing, development, and transactional processes. Finally, this procedure can be used to describe processes in which the process output is not normally distributed, which is the nature of many processes; e.g., days-sales-outstanding.

The PDF article that is available below through the “down load” button elaborates more on resolving issues with a traditional process capability study.


Process Capability Study: Business as a Whole Application

The Integrated Enterprise Excellence (IEE) Business Management System applies the article described concepts to the business as a whole.  A one-minute video describes issues with traditional scorecards, which is basically an extension of the described process capability study and resolution concepts described above and in the article.


process capability study video


A 5-book set provides the details for the implementation of the suggested enhancement to traditional process capability reporting — at all levels in an organization:


process capability study books



Contact Us to set up a time to discuss with Forrest Breyfogle how your organization might gain much from an Integrated Enterprise Excellence (IEE) Business Process Management System and its enhanced process capability study methodology.