Ppk

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.

Ppk-Eqn

where

  • USL is the Upper Specification Limit,
  • LSL is the Lower Specification Limit,
  • s is the sample standard deviation from all combined data, and
  • X-bar is the sample mean from all combined data.

Ppk is maximized by minimizing variation and increasing the distance from the nearest specification.