The FDA sets limits on acceptable insect damage in raw foods. Insect feeding damage on filbert nuts (aka hazelnuts) in the field can lead to discoloration and rancidity. Customers would not wish to purchase the nuts, but the damage can only be detected after the nuts are opened. It would be inconvenient for hundreds of customers to purchase rancid nuts and try to return them or do nothing and lose their money. Purchasing rancid nuts would hurt the market for nuts that are grown without pest damage. A consumer needs information for purchase decisions. One FDA role is to provide that information.
The FDA will inspect nuts to determine if they meet the standard, in this case, less than 10% damage. It is not possible nor practical to crack all the nuts.
What to do?
The FDA has a protocol of progressive subsampling. Out of a shipment, 100 nuts are taken at random and inspected. If 5 or fewer nuts have insect damage, the shipment meets the standard (less than 10%) and sampling stops. If 15 or more nuts have insect damage, the shipment does not meet the standard and is rejected. If the damage is between 6 and 14 nuts, more sampling is needed.
An additional 50 nuts are inspected. 10 or less and the shipment meets standards. 19 or more rejects the shipment, and 11-18 means 50 more nuts are to be sampled. Up to 7 rounds of additional sampling (500 nuts total) may be necessary. These procedures help insure our food quality, in spite of unpreventable insect damage.