15.14 Random Sampling
The units selected for inspection from the lot should be chosen at random, and they should be representative of all the items in the lot. The random sampling concept is extremely imporan in acceptance sampling. Unless random samples are used bias will be introduced. For example, the supplier may ensure that the units packaged on the top of the lot are of extremely good quality, knowing that the inspector will select the sample from the top layer. Salting a lot in this manner is not a commom practice, but if it occurs and nonrandom-sampling methods are used the effectiveness of the inspection process is destroyed