Cp/Cpk Calculation Rule
For Cp
Cp
=
(USL - LSL)
/
(6 * StdDev)
For Cpk
CpkL
=
(Mean - LSL)
/
(3 * StdDev)
CpkU
=
(USL - Mean)
/
(3 * StdDev)
Cpk
=
Min(CpkL,CpkU)
Where:
LSL
=
Lower Specification Limit
USL
=
Upper Specification Limit