Abstract
In Japanese Industrial Standards (JIS) there are variable a single sampling inspection plans having desired operating characteristics in both cases that the standard deviation is known and unknown. JIS Z 9003 (where standard deviation is known) provides two kinds of assurance criteria for lot quality ; one is for the mean in lot quality, the other is for the fraction defective in the lot. On the contrary, JIS Z 9004 (where standard deviation is unknown) is only specified in the case of assuring the fraction defective. From this viewpoint, Arizono et al. proposed a variable sampling plan which assures not only the mean but also the standard deviation in lot quality when the standard deviation is unknown. However, the design method is based on log-likelihood ratio statistics and is very cumbrous and circuitous. In this paper, by applying Patnaik's approximation to the sample data of the lot quality, a very simple method is proposed for designing a variable single sampling plan which assures both the mean and standard deviation in lot quality without log-likelihood ratio statistics, and the effectiveness of the proposed design method is verified through simulations.
