International Journal of Quality Engineering and Technology 

About: International Journal of Quality Engineering and Technology is an academic journal published by Inderscience Publishers. The journal publishes majorly in the area(s): Computer science & Control chart. It has an ISSN identifier of 1757-2177. Over the lifetime, 126 publications have been published receiving 403 citations. The journal is also known as: IJQET.

EWMA control charts for multivariate Poisson-distributed data

Abstract: Much of the research involving simultaneous monitoring of several related quality characteristics that follow a multivariate Poisson distribution has relied on using the normal approximation to the Poisson distribution in order to determine the appropriate control limits. In this paper, evaluation and implementation of MEWMA schemes for count rates using the multivariate Poisson framework itself are presented. We demonstrate that the multivariate EWMA chart-based directly on the multivariate Poisson distribution is superior to one based on normal-theory with respect to the in-control average run length. The proposed scheme performs similarly to one based on normal-theory for detecting an out-of-control process. We also illustrate a step-by-step numerical example on the practical use of the new control chart.

Development of multiple deferred state sampling plan based on minimum risks using the weighted Poisson distribution for given acceptance quality level and limiting quality level

Abstract: Since the first acceptance sampling plans have been developed 80 years ago, a number of selection principles have emerged. The majority of these principles are characterised by the fact that they look upon producer and consumer as two opposing parties. However, in many occasions, e.g., in final inspection, producer and consumer represent the same party and, therefore, the used sampling plan should not make an attempt to discriminate between their interests. In this case the interest is to avoid wrong decisions, i.e., reject product of sufficient quality and accept product of insufficient quality. Thus, the natural objective in these cases is to use overall risk for a wrong decision as optimisation criteria. Optimum result can be arrived further by the weighted Poisson distribution. In this paper, a table and procedure are given for finding the multiple deferred state-(c1, c2) sampling plan involving minimum sum of producer’s and consumer’s risks for specified acceptance quality level and limiting quality level using the weighted Poisson distribution. This is the case with so called ‘multiple deferred state-(c1, c2) sampling plan for given acceptance quality level and limiting quality level involving minimum risks using the weighted Poisson distribution’.

Analysis strategies for multiple responses in quality improvement experiments

Abstract: Quality improvement experiments often aim to find operating condition that achieves the target value for the mean of a process characteristic, and simultaneously minimises the process variability. For this purpose, Taguchi's techniques of analysis based on signal-to-noise ratios and dual response surface methodology are commonly used to achieve this goal. This paper shows how the generalised linear models approach of modelling the 'mean function' and 'variance function' jointly can be used to achieve the goal. Two examples illustrate differences among three approaches.

On the economic-statistical design of control charts constrained by the inspection workstation configuration

Abstract: A key issue for the use of control charts in a manufacturing process is the selection of their design parameters. At the moment of chart design, it is important to consider the inspection resources available at the workstation and the process operating parameters, which can strongly constrain the search for optimal chart design parameters. In this paper, the constrained economic-statistical designs of EWMA and Shewhart charts monitoring the sample mean are compared: the SPC inspection activities are locally self-managed by a worker demanded also to perform the manufacturing activities at the workstation. The shift to the out-of-control condition for the monitored quality characteristic is assumed as a random variable. A benchmark of 64 process scenarios has been generated to investigate the influence of several process operating parameters and workstation configuration. Finally, the accuracy of the expected inspection cost estimation has been computed for several distributions fitting the random shift behaviour.

A Johnson's type transformation EWMA-S² control chart

Abstract: This article demonstrates how a four parameters (bounded) Johnson SB transformation combined with an EWMA approach can be used to monitor the sample variance of a process. The resulting chart will be called an EWMA-J-S² chart. In this article, the computation of both the control limits and the parameters of the Johnson SB transformation of the EWMA-J-S² chart are explained. An easy-to-use table providing useful constants and an illustrative example are given. The distributional properties of the transformed sample variance are derived and, finally, an optimal design strategy based on the ARL is presented and a list of optimal design parameters for the EWMA-J-S² chart is provided.