For the case where the lifetime at a stress level has a Weibull distribution, statistically optimal and practical accelerated life test plans are developed under the assumptions of intermittent inspection and Type‐I censoring. For a statistically optimal plan the low stress level, the proportion of test units allocated, and the inspection times are determined such that the asymptotic variance of the maximum‐likelihood estimator of a certain quantile at the use condition is minimized. Although the practical plan adopts the same design criterion, it involves three rather than two overstress levels and easily calculated inspection schemes. Despite some loss in efficiency the practical plan has several advantages over the statistically optimal one. For instance, the practical plan can provide means for checking the validity of the assumptions made, may reduce the danger of extrapolation, and is more convenient to determine and implement. Computational experiments are conducted to evaluate the relative efficiency of a practical plan to the corresponding statistically optimal plan. Guidelines for selecting an appropriate practical plan are also described with an example.

No abstract

Industrial engineering has played a central role in creating knowledge on quality control and reliability engineering (Q&R) and delivering such knowledge to various industries. This special issue paper is prepared in celebration of the 40 th anniversary of the Korean Institute of Industrial Engineers (KIIE), and includes discussions on how Q&R areas have evolved over almost 100 years and on the current domestic and international trends of Q&R activities in industry as well as in academia. To identify academic research trends, all Q&R related papers published in the Journal of the Korean Institute of Industrial Engineers (JKIIE) and IE Interfaces are examined and classified according to their research topics. Recent Q&R related papers published in IIE Transactions are also examined and classified in a similar manner, and the papers published in KIIE journals are compared with those in IIE Transactions with respect to the research areas emphasized, yearly trend of each research area, type of systems studied, research approaches and methodologies adopted, etc. In addition, quality control activities in domestic industries are evaluated based on a recent survey conducted by Korea Productivity Center, and for domestic reliability engineering activities, government-led projects and their accomplishments over the past decade are introduced. Based on the above, recommendations are made for the future directions of academic research and Q&R activities in industry. †

In this article, we deal with a design problem for determining the levels of noise factors in the Taguchi method. First, the proposed levels by Taguchi method is reviewed in case of smaller-the-better performance characteristics. We obtain the optimal levels of noise factors minimizing the mean square error of SN(signal to Noise) ratio and compare the optimal levels with the levels proposed by Taguchi method under the first and second order models. Secondly, the concept of V-optimality is applied to determining the levels of noise factors. †

No abstract