SAE EIA 591:2015-07-01

The traditional approach to measuring levels of nonconformance using attribute data, whether the results are stated in percent or Parts Per Million (PPM), becomes more burdenson as the nonconformance levels approach zero. The quantities required to establish a data base for an acceptable confidence level may be in the hundreds of thousands, which also makes it impracticable for a user to verify these quality levels at an Incoming Inpsection facility.