Although Sampling Plans with zero acceptance numbers are fairly common in the
industry, one of the problems of a zero accept number is that the inspection log
may look like this...
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,1 ... (Oh no! A defect!).
The problem is that there is no warning that the quality is dropping or that a defect is
about to show up. Furthermore, the data, all zeros, provides no way to estimate
confidence limits around the zero percent defective estimate of the quality of the prior lots.
Sometimes, an accept number of one is better than zero even though a larger sample
size is required.
Dan Brandler.
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