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Operating Characteristic (OC) Curve For Defects Sampling Plans

BIS.Net Team

An OC curve is an important tool for the analyst to assess the protection a given sampling plan provides.

Even when a sampling plan has been derived scientifically using BIS.Net Acceptance Sampling, the OC Curve provides additional insights over the complete range of possible defects per 100 units

For example, when deriving a sampling plan only two levels of defectives are considered, the Acceptable Quality Level (AQL) and Lot Tolerance Percent Defects (LTPD).

Consider the example where we specify an AQL of 3%, LTPD of 6% with a Producer’s risk of 5% and Consumer’s Risk of 10%. We would obtain the following sampling plan with near matching producer’s and consumer’s risks at the specified AQL and LTPD.

The OC Curve however allows the analyst to see what the risk of accepting a batch at different levels of defectives is. For example, at 5 defects per 100 units, slightly less than the specified LTPD of 6 defects per 100 units, the risk of accepting such a batch is 30%, three times as high as the specified 10%. This may not be satisfactory. If not, then an alternative sampling plan can be trialed with the BIS.Net Acceptance Sampling App.