Economic efficiency of AOQL variables sampling plans

Sampling inspection is a quality control tool used in industry to keep the quality of the products at satisfactory level while at the same time having the cost in control. When using acceptance sampling inspection, a decision on whether the lot of items is to be accepted or rejected is based on results of inspecting a sample of items from the lot. Rectifying acceptance sampling plans minimizing mean inspection cost per lot of the process average quality were designed by Dodge and Romig for the inspection by attributes. Plans for the inspection by variables were then proposed and such plans may be more economical than the corresponding attributes sampling plans. The recently proposed plans using EWMA statistic may lead to further improvements in the inspection cost. The design of the EWMA-based rectifying AOQL sampling plans minimizing the mean inspection cost per lot of process average quality is recalled. The measure for assessing the comparative economic efficiency of the plans, which may be used for getting a guidance for selecting the most appropriate type of the sampling plan to be used, is proposed and the economic characteristics evaluation of the plans is shown.