A lot inspection sampling plan based on EWMA yield index

Abstract

In this paper, a new variable sampling plan using the exponentially weighted moving average (EWMA) statistic based on the yield index is developed for lot sentencing. The proposed plan considers the quality of the current lot as well as the preceding lots through the EWMA statistic. The sample size and the critical value of the proposed plan are determined by considering the acceptable quality level at the producer's risk and the lot tolerance percent defective at the consumer's risk. The plan parameters are tabulated according to the smoothing constant of the EWMA statistic and various combinations of two risks. An example is provided for illustrating the proposed plan.