Savings of the Inspection Cost in Acceptance Sampling

This paper refers to the rectifying sampling inspection plans with given lot tolerance percent defective (denoted LTPD). The LTPD sampling plans minimizing mean inspection cost per lot of process average quality, when the remainder of rejected lots is inspected, were originally designed by Dodge and Romig for inspection by attributes (each inspected item is classified as either good or defective). The corresponding rectifying plans for inspection by variables were created by author of this paper. Comparison of these two types of the LTPD plans from economical point of view is presented herein. Using the LTPD plans by variables we can reach fundamental savings of the inspection cost. In this paper we analysed the situations in which the rectifying LTPD plans by variables are more economical than the corresponding attribute sampling plans. A criterion for deciding if inspection by variables is to be used instead of inspection by attributes is suggested and calculated for input parameters of acceptance sampling