Cp index

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Cp index is a statistical measure of process capability. This means that it is a measure of how capable a process is of producing output within specification limits. This measurement only has meaning when the process being examined is in a state of statistical control. Cp disregards centering, and is insensitive to "shifts and drifts" (special cause) in the data. If the process mean is not centered within the specification limits, this value may therefore be misleading, and the Cpk index should be used instead for analyzing process capability:

(where USL is Upper Spec Limit and LSL is Lower Spec Limit and sigma is the standard deviation of the process)

[edit] See also

• Common cause and special cause
• Control chart