Examples of average quantity system testing

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AQS tests for weight and volume

In Table 3, 3 500 packs of butter are identified as the inspection lot. Using Table 1, 125 packs of butter are chosen at random as the sample or threshold. Table 2 shows that a 500 g net package is allowed a T of 3% or 15 g. Therefore an inadequate package (T1 error) is allowed to contain between 485 g and 470 g.

A package weighing less than 470 g would be more than twice the tolerable deficiency and would fail rule 3 (T2 error). The reference test identifies two inadequate packages, no packages with a T2 error and an average net weight of 501 g. Therefore the packs of butter pass all three rules.

If potatoes had been chosen from Table 3, an inspection lot of 148 would have resulted in a sample or threshold size of 50 packages. Table 2 indicates a T of 1.5% (45 g) for a 3 kg bag. The reference test identifies no inadequate T1 packages and one inadequate T2 package. The inspection lot fails the reference test because of the one inadequate T2 package when none are permitted under rule 3.

Table 3 Examples of reference tests for weight or volume

Product Quantity Lot size Sample size Sample average Number of inadequate T1 packs Number of inadequate T2 packs Pass or fail
Butter 500 g     3500 125 501g 2 0 P
Wine 750 mL 130 50 752mL 0 1 F
Sugar 1.5 kg 5000 125 1.6kg 4 0 P
Potatoes 3 kg 148 50 3.1 kg 0 1 F

AQS tests for number

Consider packages of oysters labelled ‘12 Pacific oysters’. There are a total of 150 packs which make up the inspection lot. Therefore, using Table 1, 50 packages must be chosen at random to form the sample.

Testing identifies that 49 out of 50 packages contain a dozen oysters and one package contains 11 oysters. This means the inspection lot fails because under Table 2 no deficiency is allowed.

A second example involves the inspection of mild steel washers. Each of the 500 packages contains 200 washers, according to their labels. Therefore the sample size is 50 packages chosen at random. Testing identifies five packages that contain 197 washers. Table 2 shows that the tolerable deficiency for packages containing more than 50 items is the nominal quantity (Qn) x 1% (T = 200 x 1%) or two items. Because the number of inadequate T1 packages permitted would be three (using Table 1) the lot fails the reference test.