Sigma level
Six Sigma performance scale
Z = 3 · Cpk; DPMO = Φ(−(Z − 1.5)) · 10⁶
The number of standard deviations between the process mean and the nearest limit. By Six Sigma convention a long-term shift of 1.5 sigma is assumed, so a 6 sigma process corresponds to 3.4 defects per million opportunities.
Calculate it
Cpk, PPM and Sigma Converter: Convert Cpk, PPM, yield and sigma level, with or without 1.5 σ shift.