What percentage of products in a Six Sigma process are technically defect-free?

In a Six Sigma process, the goal is to achieve a defect rate of fewer than 3.4 defects per million opportunities. This corresponds to a process capability of 6 standard deviations from the mean, which is where the term "Six Sigma" originates.

To translate this defect goal into a percentage of products that are technically defect-free, the calculation begins by considering that if there are 3.4 defects per million, then the number of defect-free products would be 999,996.6 out of 1,000,000. When calculated as a percentage, this results in approximately 99.99966% of products being defect-free.

This high level of quality is what sets Six Sigma apart from other quality management methodologies, as it not only focuses on reducing defects but also on achieving near perfection in processes.