Sequential sampling plans for early-life reliability assessment

This paper proposes a method for demonstrating early life reliability by combining environmental stress screening strength models and Wald´s sequential test for equipment whose early life reliability is described by a Weibull distribution of time to failure. The proposed method uses screening strength models to transform an environmental stress test (e.g. temperature cycling/random vibration) to an equivalent constant heat test. This transformation gives an equivalent number of field operating hours which can then be used together with the Weibull model of early-life reliability to compute the accept and reject boundaries of Wald´s sequential test plan. This method helps an equipment supplier decide whether a product meets a customer´s requirement of early-life reliability