Three Sigma quality level corresponds to what percentage of specification compliance?

• A. 93.32% specification compliance (67,000 defects per million)
• B. 99.999% specification compliance (3.4 defects per million)
• C. 95% specification compliance (50,000 defects per million)
• D. 0% specification compliance

Answer: (A)

The key idea is how a sigma level translates to how much of the output meets specifications. At a three-sigma level, about 99.7% of results fall within specification, which corresponds to roughly 2,700 defects per million opportunities (DPMO). In other words, a three-sigma process is expected to produce very few defects, with most items conforming to the specification limits.

Among common mappings, a much higher quality level—six sigma—relates to about 99.9997% specification compliance (around 3.4 DPM). A 95% compliance figure (about 50,000 DPM) would indicate a poorer performance than three sigma, while 0% is not plausible for a manufacturing process.

So, in standard terms, three-sigma corresponds to roughly 99.7% specification compliance (≈2,700 DPMO). The option stating 93.32% compliance (67,000 DPM) would imply a defect rate far higher than three-sigma.