Numerous Sigma Level Tables Need Correction: Commonly Used Tables Ignore Permitted “Left-Side” Defects

Many popular textbooks in the fields of operations management and quality contain process sigma level tables that are slightly inaccurate and inconsistent among each other. These discrepancies annoy and are confusing to fastidious educators and students and could lead to minor estimation errors in practice. We document instances of the error and provide explanation, calculations, and an accurate sigma level table.