SPC基本認識(ppt 12)

Ppk 與 Cpk 之差異
Ppk
The 6 range of a process’s total variation, where is usually estimated by the sample
standard deviation

--This is the variation due to both common and special cause.
Cpk
The 6 range of a process’s inherent variation, for statistically stable processes only, where is usually
estimated by

--That portion of process variation due to common causes only.

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