Ppk - Assessing Overall Performance without Targets
When no target is given, Ppk is used as the primary performance measure in place of Ppm. Ppk may be calculated as follows.
- USL is the Upper Specification Limit,
- LSL is the Lower Specification Limit,
- s is the sample standard deviation from all combined data, and
- is the sample mean from all combined data.
Ppk is maximized by minimizing variation and increasing the distance from the nearest specification.