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Statistical Process Control (SPC)
Fred Allen

According to many, Six Sigma is based on Statistical Process Control (SPC), a method of visually monitoring production processes. In Six Sigma, each business process must be measured and for this often the SPC methodology is used. Aims of SPC are: 1. Adjustment: To detect quickly when a process needs readjustment or repair. 2. Improvement: To find the most urgently needed improvement in the system itself. (...) Read more? Sign up for free

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PC
Alice


What is the difference between PPK & CPK?



Cpk or Ppk??
JacquesAlain TIAKO, Manager, France, Member


Cpk  It's the capability index for a stable process (the process must be in a state of statistical control). The sigma calculation is based on within subgroup variation.
Ppk  It's the performance index (the actual process PERFORMANCE). The estimate of sigma is based on total variation. Ppk must be calculated if less than 100 samples or when the process is chronically unstable but meeting the specifications and in a predictable pattern.

