Variables two stage sampling plans based on the coefficient of variation

The coefficient of variation (CV) is an important quality parameter to measure the stability of the product quality. A variable two stage sampling plan based on the CV is developed in this paper when the quality characteristic follows normal distribution. The optimal plan parameters of the proposed variable two stage sampling plan are determined by minimizing the average sample number (ASN) using the two-point approach on the operating characteristic (OC) curve, and then tabulated for various combinations of acceptance quality level (AQL) and limiting quality level (LQL). The efficiency of the proposed variable two stage sampling plan is compared with the existing variable single sampling plan. The results show that the proposed plan has better performance than the single sampling plan in terms of ASN. Finally, the proposed plan is illustrated with a practical example.