Shifting the specification limit by one-half sigma will change the Cp ratio by 0.0833 and might change the Cpk ratio by 0.1667. These ratios are intended as an aid to understanding, rather than a hurdle to be overcome. Converting them into fractions nonconforming is less helpful than converting them into dollars.
donwheeler 9/5/2001
Shifting the specification limit by one-half sigma will change the Cp ratio by 0.0833 and might change the Cpk ratio by 0.1667. These ratios are intended as an aid to understanding, rather than a hurdle to be overcome. Converting them into fractions nonconforming is less helpful than converting them into dollars.