When a process functions at a Six Sigma level, how many defects per million opportunities does it correspond to?

When a process operates at a Six Sigma level, it achieves a remarkable level of quality, corresponding to just 3.4 defects per million opportunities. This metric is foundational to the Six Sigma methodology, which aims to minimize variability and defects in processes. The concept of Six Sigma is grounded in statistical analysis and defines the process capability in terms of the number of standard deviations (sigma) between the mean and the nearest specification limit.

At Six Sigma, the process is expected to fall within the limits of design specifications 99.99966% of the time, leading to a very low number of defects. This high standard of performance indicates that for every million opportunities for defects to occur, only 3.4 defects are expected on average. This demonstrates an emphasis on continuous improvement and quality control in processes to enhance customer satisfaction and operational efficiency.

Understanding this context highlights why the figure of 3.4 defects per million opportunities is critical for organizations striving for excellence through the Six Sigma approach.