Wei, Z., Rebandt, R., Start, M., Gao, L. et al., "Approaches to Achieving High Reliability and Confidence Levels with Small Test Sample Sizes," SAE Int. J. Commer. Veh. 8(2):343-354, 2015, doi:10.4271/2015-01-2758.
In product design and development stage, validation assessment methods that can provide very high reliability and confidence levels are becoming highly demanded. High reliability and confidence can generally be achieved and demonstrated by conducting a large number of tests with the traditional approaches. However, budget constraints, test timing, and many other factors significantly limit test sample sizes. How to achieve high reliability and confidence levels with limited sample sizes is of significant importance in engineering applications. In this paper, such approaches are developed for two fundamental and widely used methods, i.e. the test-to-failure method and the Binomial test method. The concept of RxxCyy (e.g. R90C90 indicates 90% in reliability and 90% in confidence) is used as a criterion to measure the reliability and confidence in both the test-to-failure and the Binomial test methods. For the test-to-failure method, high reliability and confidence levels are achieved by using historical data and the Bayesian statistics approach. For the Binomial test method, the high levels are achieved through extending test time and accelerating tests by increasing the stress/load level. With these methods, high reliability and confidence levels, such as R99C99 or higher, can be achieved with small sample sizes.