Accelerated Life Test Plans for Predicting Warranty Cost

Warranty is an important sales feature for many products, especially consumer products. Manufacturers usually want to predict the warranty cost as early as possible for various purposes. This can be done by using the accelerated life tests conducted in the early stages of the product life cycle. This paper describes a method for predicting the warranty cost, and its confidence interval for a product population that will experience varying stress levels in the field. The paper also presents 3-level best compromise accelerated life test plans. The plans choose the optimal values of the low stress level and the corresponding sample allocation to minimize the asymptotic variance of the maximum likelihood estimate of the warranty cost. An application example is presented to illustrate the test plans. The test plans are robust against the misspecification of the warranty length, and other parameters.