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There are many studies on standby redundant systems, since those are the most standard models for ensuring reliability in systems. Particularly, two-component priority standby redundant systems are...

The (x¯,s) control chart is one of simultaneous control charts to monitor process mean and variance on x¯-s coordinate. The primary purpose of the (x¯,s) control chart has been the judgement of the...

The proportion of non-conforming items has been traditionally utilised as an evaluation criterion for quality of items. However, the proportion of non-conforming items is not necessarily useful as a proper evaluation criterion for controlling high-quality manufacturing in recent years. Accordingly, in order to achieve further quality improvement and innovation, more careful quality evaluation has been required newly. Then, a concept of quality loss in the Taguchi methods has been devised as a severe criterion of quality evaluation. Hereby, a variable single sampling plan having desired operating characteristics (OCs) indexed by quality loss has been proposed in the area of statistical quality control. By the way, the most economical sampling inspection in the average sample number (ASN) is the sequential sampling plan based on the Wald’s sequential probability ratio test. Then, from the viewpoint of cost reduction, we discuss a variable sequential sampling plan having desired OC indexed by quality loss wi...

There are some conventional attribute sampling inspection plans designed with respect to attribute property, such as the proportion of nonconforming items. Among them, the attribute sampling inspection plans with screening are defined under the lot tolerance percent defective (LTPD) inspection scheme and the average outgoing quality limit (AOQL) inspection scheme. On one hand, Taguchi has proposed the concept of quality loss as a measure to evaluate the quality of items based on the variable property instead of the traditional attribute quality evaluation. Hereby, in this article, the design procedures for variable sampling inspection plans with screening indexed by Taguchi’s quality loss in conformity with the conventional attribute sampling inspection plans with screening composed of the LTPD and AOQL inspection schemes are represented.

Assume that lot quality characteristics obey a normal distribution. Kanagawa et al. have proposed the ( x, s ) control chart which enable the user to monitor both changes of the mean and variance simultaneously. Further, the results of Watakabe and Arizono enable the user to evaluate the performance for out-of-control state in the case of using the ( x, s ) control chart. On the other hand, Taguchi has presented an approach to quality improvement in which reduction of deviation from the target value is the guiding principle. In this approach, the loss is expressed as a quadratic form with respect to the difference between the measured value x of a product characteristic X and the target value T of a product quality characteristic. Then, we can evaluate the process quality based on the Taguchi's loss criterion. We consider here the economical operation of the ( x, s ) control chart in conformity with the expected total operation cost function based on the sampling cost and the loss due to derivation in the...

The cumulative sum (CUSUM) control chart is known as a sensitive control chart to a slight change of the process quality characteristics. This control chart is designed based on a series of cumulative sum of the statistic derived from data. For normally distributed characteristics, it should be needed to monitor both changes of the mean and variance simultaneously. However, it is difficult to design the CUSUM or joint control chart using the statistics of and s or R jointly. By the way, Kanagawa et.al . have proposed the ( )control chart which enables the user to monitor both changes of the mean and variance simultaneously based on one statistic for normally distributed characteristics. When the CUSUM control chart is considered based on the ( ) control chart, it is possible to design and use the CUSUM control chart more easily than the joint CUSUM and either R or s control charts. Hence, we consider a CUSUM ( ) control chart in order to improve the performance for a slight change of the process quality c...