Because there is not a lot of historical data we take large samples from the process to account for variation. Generally you use this when a process is too new to determine if it is under statistical control. Pp and PPk are used for Process Performance. Process capability uses the process sigma value determined from either the Moving Range, Range or Sigma control charts. This often happens with a mature process that has been around for a while. Generally you use this when a process is under statistical control. Cp, and Cpk are used for Process Capability. In both cases we want to try to verify if the process can meet to meet Customer CTQs requirements. Pp and Ppk are called Process Performance. Vw 01m transmission problems solvedĬp and Cpk are called Process Capability. This will help me make the article even better for you.Īgain, this will help me make the article better for you and everyone else. If you are not finding what you are looking for, please let me know in the notes below. There are also crib notes on what the equations mean in a real performance sense, what you should be able to tell about a process depending on Cp and Cpk values and more. In other words, it allows us to compare apple processes to orange processes! This is a long article, but I thought it was important to keep Cp and Cpk together.Ĭpk is addressed first, then Cp. In Six Sigma we want to describe processes quality in terms of sigma because this gives us an easy way to talk about how capable different processes are using a common mathematical framework. Cp and Cpk are considered short-term potential capability measures for a process.