• Journal of Korean Institute of Industrial Engineers
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• v.41 no.1
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• pp.115-120
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• 2015

Evaluating product quality level is necessary before the manufactured items are delivered to the customer. When the amount of the items to be manufactured is limited and the product is of high price and should be evaluated by destructive testing, the number of samples to be tested should be as small as possible. This paper presents a small-sample inspection method using hyper-geometric distribution and Bayesian approach for finite small-sized population. A method of determining the minimum sample size is presented for given population size, allowable number of defectives, warranteed defective level, and confidence level which is the degree of confidence on the product quality level recognized by both the producer and the customer.

• Journal of Korean Society for Quality Management
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• v.17 no.1
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• pp.89-106
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• 1989

For Weibull distributed lifetimes, this paper presents asymptotically optimal accelerated life test plans for practical applications under intermittent inspection and type-I censoring. Computational results show that the asymptotic variance of a low quantile at the design stress as optimal criterion is insensitive to the number of inspections at overstress levels. Sensitivity analyses indicate that optimal plans are robust enough to moderate departures of estimated failure probabilities at the design and high stresses as input parameters to plan accelerated life tests from their true values. Monte Carlo simulation for small sample study on optimal accelerated life test plans developed by the asymptotic maximum likelihood theory is conducted. Simulation results suggest that optimal plans are satisfactory for sample size in practice.

• Journal of Korean Institute of Industrial Engineers
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• v.41 no.5
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• pp.481-487
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• 2015

In the product development stage, it is very important to ensure demanded quality level before moving to the full-scale manufacturing. For example, in developing guided weapons, live-fire tests are required to verify the final performance of the weapons which are very expensive. The quality evaluation of the guided weapons needs destructive testing, which makes it necessary to test as small number of samples as possible. This paper presents sampling inspection plans and calculating system for finite population guided weapons, which can meet the demanded quality level and confidence level with the minimum number of performance tests. The result of this paper can be useful for any kind of costly destructive testing.