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Sampling Plan Analyzer Help System 

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Protection

The protection provided by a sampling plan is primarily described by the OC curve of the sampling plan. For most sampling plans the protection is constant and the OC curve alone is adequate. For a few sampling plans the protection varies depending on the circumstances and multiple OC curves are required including the Stationary OC Curve, Maximum OC Curve and Minimum OC Curve.

While the OC curves provide a detailed description of the protection, the protection can be adequately summarized using the AQL and LTPD when the protection is constant. When the protection varies one needs in addition the Max OC(LTPD) - Maximum Probability of Acceptance at LTPD, Min OC(AQL) - Minimum Probability of Acceptance at AQL, Rate of Convergence at LTPD, and Rate of Convergence at AQL.

The OC curves describe the protection for individuals lots. When inspecting a long series of lots, the AOQ curve and AOQL can also be used to further describe the behavior (protection) of the sampling plan.