![]() ![]() A good analogy is parking a car in a garage. It can be used to establish baseline for the process and measure the future state performance of the process for comparison.Ĭp for processes that are under statistical control and Pp for new processes. Process Capability Analysis tells us how well a process meets a set of specification limits, based on a sample of data taken from a process. What Can Process Capability and Process Performance Tell Us? In Cp we are assuming a stable process and will likely have enough data to calculate a true standard deviation. Pp we use sampling and have to calculate an estimated standard deviation of the sample. The biggest difference between Cp and Pp is how the Standard Deviation is determined. When to use Pp Ppk Cp Cpk Differences Between Cp & Pp To determine the answer to those questions we see how wide the process dispersion (spread of values) and how centered the process is relative to those specifications. ![]() To begin to answer these questions it all starts with customer requirements and the follow up with what we know mathematically about the variation of the process.Ĭp, Cpk, Pp and Ppk are all parameters (indices) that can help us to understand how our process is operating relative to the specifications, or in other words, they measure how close our process is running to its specification limits.įor requirements we measure the process specifications. If you’d like more depth including calculations, etc, see these articles: This article deals with an overall examination of Process Capability & Performance (Pp, Ppk, Cp, Cpk). Is a process capable? Is the process acceptable? How is the process actually behaving vs how it theoretically could be behaving? These are questions you can ask during a DMAIC project during both the measure phase (if you have good, existing data) or in the control phase after you have implemented your changes. Cp, Pp, Cpk, and Ppk are capability and performance indicators for your process. ![]()
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