Understanding how Cp & Cpk are used to ensure quality Page 4 of 4 146-008 Glossary Standard Deviation Standard deviation is denoted by the Greek symbol Sigma (?) and is computed by the following formula: Where X is the individual values for a sample of size n. To Ppk or Not to Ppk. And here is where the danger lies in only reporting Cpk and forgetting about Ppk like it's George Michael's lesser-known bandmate (no offense to whoever he may be). We can see from the examples above that Cpk only tells us part of the story, so the next time you examine process capability, consider both your Cpk and During this tutorial, characters you are to enter in a field will be enclosed in brackets < >. Do not type the brackets themselves, just the information between them. We are now prepared to create a file with Quickie98. Cpi and Ppi will be equal to Cpk and Ppk if the process perfectly Process Capability What it is Process Capability looks at short term capability and long term performance of a process with regard to customer specifications. Standard indexes are used: Cp, Cpk, Pp and Ppk. These can be converted into ppm. A simple view of Process Control and Process Capability In the last post we looked at the different process capability indices like Cp, Cpk, Cpm etc. But there is also Pp and Ppk indices that measure process performance. There is a fundamental difference between the two types of indices. We will now try to understand the difference between process capability and process performance. Differences Between Cpk and Ppk Statistics . Last Revised:08/09/02 By: AVI . Key Words: Cpk, Ppk, differences, statistics Purpose: This document describes the differences between Cpk and Ppk values. Cpk vs. Ppk values: Cpk values are known as "process capability" measures. Measurement of Process Capability: Cp, Cpk, Pp, Ppk, Probability Plotting, and Six Sigma * Forrest W. Breyfogle, III Smarter Solutions Inc., Austin, Texas Process capability and process p