One puzzling aspect of the "official" Six Sigma literature is that it states that a process operating at Six Sigma will produce 3.4 parts-per-million (PPM) defects. However, if a special normal distribution table is consulted (very few go out to Six Sigma) one finds that the expected defects are 0.002 PPM (2 parts-per-billion). Find out the reason behind this discrepancy.