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Automatic test equipment for 100 percent incoming inspection of electronic devices is inexpensive enough and effective enough today that sample testing no longer makes sense for most quality-control organizations. Although component manufacturers normally perform 100 percent inspection--at least in the early stages of manufacture--there are a great many ways in which errors can be passed along to the user. As a result, incoming digital integrated circuits (IC's) may have error rates as high as 5 percent and, for linear ICes, rejection rates may be up to 10 percent. Nor do acceptable quality levels (AQL's) provide a positive assurance of the quality of a lot, as is pointed out in an appendix. Break even is basically the point at which the cost of testing meets the cost of not testing. It is often expressed as the number of units that must be tested per year to justify a piece of automatic test equipment. Both the cost of testing and the cost of not testing can be calculated quite easily once the various factors to be used are considered.