Six Sigma Methodology: Defects per Million Opportunities | 6σ Explained

The correct answer is 3-4. In the Six Sigma methodology "good enough" is represented by an error rate of 3.4 defects per million opportunities, of six standard deviations (6σ) from the mean, or 99.997 percent error free, as shown in exhibit 10.7. Relying on human accuracy only, one might expect ten defects per hundred opportunities, or 100,000 errors per million opportunities, versus 3.4 if 6σ is achieved (Total defects ÷ Total opportunities × 1,000,000). In a normal distribution, Six Sigma would represent how many defects per million attempts?