Equations for Cp Cpk Pp Ppk calculation are not difficult; however, it is VERY important to know the details behind the equations, which are described in this recorded webinar.
Cp Cpk Pp Ppk Calculation
To reiterate,the equations are not difficult to determine calculate the process capability indices of Cp Cpk Pp Ppk. For example,
where USL is an upper specification limit, LSL is a lower specification limit, mu is mean, and sigma is standard deviation.
But organizations need to be aware of these process capability reporting issues and take appropriate action as needed. One of the big issues is how standard deviation is calculated from a process. Sounds simple — right? But there is more to it than what one might initially think, which can make a BIG difference in calculated values!!
More information about process capability equations and issues is available in “Resolving Process Capability Index Issues For Cp, Cpk, Pp, Ppk“.
Cp Cpk Pp Ppk Calculation and Gage R&R
In Lean Six Sigma, much training effort is spent on conveying the importance of having a measurement system so that consistent and correct decisions are made relative to part quality and other assessments. Measurement Systems Analysis (MSA) and Gage R&R study (Repeatability and Reproducibility) are an integral part of the Lean Six Sigma Black Belt and Green Belt training.
It should be the goal of every organization to achieve the three Rs of business; i.e., everyone doing the Right things, and doing them Right, at the Right time. One tool that provides direction for achievement of the three Rs goal is process performance metrics; i.e., a process’ performance report-out should lead to the most appropriate action or non-action. This objective is not unlike an inspection gage MSA, which is to determine if inspectors can adequately determine whether a manufactured component should be accepted or rejected.
Because of this performance-reporting need, it would seem that management and practitioners would be assessing how well current scorecard and metric reporting systems are doing from a MSA conceptual point of view. However, this does not seem to be occurring. The question is why do we not examine business metrics and process capability indices reporting from a MSA point of view with the same level of intensity that we do for product quality metrics?
This one-hour Webinar will explain more on the magnitude of the issue: we’ll give focus to how Cp, Cpk, Pp, and Ppk process capability indices’ reporting is sensitive to how a given process is sampled; i.e., an MSA issue. A predictive metric reporting system will then be described for overcoming not only the issues of process capability indices but general business-performance scorecards.
Cp Cpk Pp Ppk Calculation and Understanding: A Webinar that Provides Important Details
30,000-foot-level Alternative to address Cp Cpk Pp Ppk Calculation Issues and Confusion (Described in the Webinar)
The benefits of using 30,000-foot-level reporting as an alternative to Cp, Cpk, Pp, and Ppk process capability reporting are numerous.
An example 30,000-foot-level report-out is:
Note how the left graph uses an individuals chart to assesses process stability from a high-level point of view.
The 30,000-foot-level individuals charts are not designed to “control” a process. The x-axis may be weeks, months, or batches, for example.
The normal probability plot to the right has a straight line fit; hence, one believes the normal distribution is a good model for a capability assessment of this process output response.
The specifications of 72-78 are shown in the probability where the total percentage estimate above and below these spec limits is the estimated non-conformance rate not only now but in the future (unless something were to be improved in the process).
This estimated non-conformance rate of 17.398% is then reported at the bottom of the chart. NOTE how this statement is MUCH easier to understand than a set of Cp Cpk Pp Ppk calculation results.
30,000-foot-level Reporting at the Business Level
When 30,000-foot-level performance metrics are integrated as part an Integrated Enterprise Excellence (IEE) business management system, there are even more benefits.
The IEE system with 30,000-foot-level reporting can address the business scorecard and improvement issues that are discussed in the one-minute video:
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 30,000-foot-level metric reporting approach for addressing Cp Cpk Pp Ppk calculation issues.