Expert Answers: ANSI/ASQ Z1.4 vs. ANSI/ASQ Z1.9

My organization uses ANSI/ASQ Z1.4 and requires suppliers to use that or a more stringent sampling plan. We have a supplier using ANSI/ASQ Z1.9. How do the plans compare, particularly regarding stringency on accept and reject numbers?

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Z1.4 is typically used for “attributes” sampling, more of a go-no-go inspection, and there are several “levels' of sampling depending on consideration for the product quality history as delivered to a given Customer plus additional consideration for the significance of the defect(ives) [Critical, Major or Minor]

Z1.9 is used for sampling of ”Variables" and is generally considered more difficult to implement and manage as each characteristic of interest must be sampled and analyzed separately

If you have access to The Certified Quality Engineer's handbook [Burke and Silvestrini] there is a reasonable overview with a couple of examples. Hope this helps!