Abstract
In Japanese Industrial Standards (JIS) is provided the single sampling inspection plans having desired operating characteristics by variables in both cases that the standard deviation is known and unknown. JIS Z 9003 (standard deviation known) provides two kinds of assurance criteria for lot quality ; the one is for the mean in lot quality, the other is for the fraction defective of the lot. On the contrary, JIS Z 9004 (standard deviation unknown) is only specified in the case of assuring the fraction defective. In this paper, we study to assure the mean in lot quality when the standard deviation is unknown. In this case it is necessary to assure both the mean and the standard deviation in lot quality, simultaneously. This paper deals with a design problem of single sampling plans by variables for the purpose of assuring both the mean and the standard deviation in lot quality.
