To illustrate the use of the OC Curves (AQL 6.5) let it be assumed that a lot is 10 percent defective. A lot
with 6.5 percent defectives will be accepted approximately 95 percent of the time, the frequency of
acceptance increasing as the percent defective decreases. However, the 10 percent defective lot fails to measure up to requirements, and while it may be a marginal lot, it may not be acceptable. An examination
of the OC curves shows that a sample size of 6 (curve E) will accept this marginal lot 88 percent of the
time; a sample size of 84 (curve M) is somewhat better, accepting the lot 65 percent of the time.
If, on the other hand, the lot is 30 percent defective, a sample size of 6 (curve E) will accept the lot only 42
percent of the time, whereas a sample size of 21 (curve J) will accept such a lot only 8 percent of the time and a sample size of 84 (curve M) will always fail such a lot.