A comparison of sequential probability ratio and generalized attributes acceptance sampling plans

Abstract

A comparison is made between Wald's Sequential Probability Ratio sampling plan, several generalized attributes acceptance sampling plans, and a curtailed single sampling plan. The evaluation of the plans is based upon a cost function based upon a combination of the Average Sampling Number (ASN) and the variance of an estimator for the proportion of defective items in a lot. Using a numerical calculation of the defined cost function, the curtailed single sampling plan and also a generalized attributes acceptance sampling plan are shown to be better than Wald's SPR in a number of instances for representative operating characteristics. However, strictly in terms of ASN Wald's SPR is shown to be better. A computer program is devised which gives a good approximation of the variance of the estimator used for Wald's SPR.