SPC基本认识(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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