What-If and Scope

Centered Mean What-If

Moving the mean to the center changes the side indexes exactly.

highlighted = computed this step

Centered Mean

The what-if mean is 50.

what-if mean=50\text{what-if mean} = 50
Centered mean what-ifThe table recomputes side indexes and Cpk when the mean is centered.centered mean what-ifvaluemean50Cpu5/3Cpl5/3Cpk5/3gain1/3

Centered Cpk

The centered what-if has equal side indexes.

Cpu=5/3Cpl=5/3Cpk=5/3\text{Cpu} = 5/3\quad\text{Cpl} = 5/3\quad\text{Cpk} = 5/3
Capability snapshotThe chart compares the base mean with 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

Cpk Gain

The Cpk gain is 1/3.

5/3−4/3=1/35/3 - 4/3 = 1/3
Capability snapshotThe chart compares the base mean with 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