IV.C.7 Process capability
Process capability is the range within which a process is normally able to operate given the inherent variation due to design and selection of materials, equipment, people, and process steps. Knowing the capability of a process means knowing whether a speciﬁcation can be held if the process is in control.
More simply put, process capability is a measure of how well normal process variation fits in the specification limits. There are a couple rules to follow for process capability to work for you:
- The process must be normal before you can make an accurate prediction of process capability.
- The sample size needs to be big enough to approximate a normal distribution. A capability study should be based on a sample of at least 30 measurement values from the process.
Quality Management BOK Reference
IV Quality Management Tools
IV.C Measurement: Assessment and Metrics
IV.C.7 Process capability - Recognize process capability (Cp and Cpk,) and performance indices (Pp and Ppk).
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