CCpk

An index of potential process capability, calculated with data from subgroups in your study. CCpk compares the process spread to the distance between a specification limit and one of the following values:

·    The process target, if one is specified, or

·    The center of the specification spread, if you provide both the upper and lower specification limits, or

·    The process average, otherwise

Compare your CCpk value to a benchmark to determine whether to improve your process; many industries use a benchmark value of 1.33.

For example, the process below has an unacceptable CCpk value; it has such a wide spread that even when the mean is on target, the process violates both specification limits.