Cp and Cpk

Cpk

Cpk checks the closer side of the spec band.

highlighted = computed this step

Cpu

Cpu measures the upper side.

(60−52)/6=4/3(60 - 52) / 6 = 4/3
Side indexesThe table recomputes Cpu, Cpl, and Cpk.side indexesvalueCpu4/3Cpl2Cpk4/3

Cpl

Cpl measures the lower side.

(52−40)/6=2(52 - 40) / 6 = 2
Side indexesThe table recomputes Cpu, Cpl, and Cpk.side indexesvalueCpu4/3Cpl2Cpk4/3

Cpk

Cpk is the smaller side index.

min⁡(4/3,2)=4/3\min(4/3,2) = 4/3
Capability snapshotThe chart shows Cp, Cpk, and the centered what-if.process capability Cp and CpkCp 5/3; Cpk 4/3; sigma 2measurevaluemeaningspec width20USL minus LSLsix-sigma width12six times sigmaCp5/3width comparisonCpu4/3upper sideCpl2lower sideCpk4/3smaller sidebaseLSL 40USL 60mean 52Cpu 4/3; Cpl 2what-ifLSL 40USL 60mean 50Cpu 5/3; Cpl 5/3Cp 5/3base Cpk 4/3what-if Cpk 5/3what-if Cpk 5/3; gain 1/3deterministic process-capability arithmetic only