You are correct in that PMI does mean different things to different people. In the forum of materials supply, some of our customers insist our own testing is per roll, per batch or per shipment or combinations of certain tests are done per roll, others per batch etc. With monitoring our own SPC and sharing that with our customers, in some cases, our customers have removed the need for their own goods inwards inspection as they have access to the results and SPC we generate on their product. I would say it depends on how statistically consistent the product is made and the test specification limits are. Hence the variability from person to person as to what it means. Depends on the supplier-customer relationship.