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.

PPK is measured by unknowed process, cpk is measured by stable process

Jacques-Alain TIAKO Manager, France

Cpk or Ppk??

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.

Ger de Waard Management Consultant, Netherlands

What is the Difference Between PPK & CPK?

In the Six Sigma quality methodology, process perf (...)