Gatlin Education Six Sigma Green Belt - OVERVIEW Why Do Six Sigma - Page 8

DPMO and Sigma Level This graphic shows how defect rates relate to a Sigma Level. As you can see, if we can define a defect rate, then the sigma level is directly calculated. Notice that the y-axis is logarithmically scaled. As we increase in Sigma Level, the Defects per Million Opportunity, or DPMO, decreases exponentially. For example, as we move from 2 Sigma to 3 Sigma, the DPMO drops from 67 thousand to 65 hundred, then to just over 200 at 5 Sigma. Which brings to mind an important aspect of the process improvement effort: while moving from 3 Sigma to 4 Sigma yields a significant improvement in customer satisfaction, moving beyond 4 or 5 Sigma involves squeezing every last drop of potential defect. Six Sigma is truly a significant achievement.