Operating Characteristic (OC) Curve For Defects Sampling Plans

The BIS.Net Team 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.

Sampling Plan - Img1
Sampling Plan - Img2

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.