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Abstract
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Due to advancing technology and manufacturing processes, the products and devices are becoming highly reliable. To obtain the information about the lifetime distribution of these products, a standard life testing method at normal working con ditions is impractical when the product has a substantially long lifespan. This problem is solved by accelerated life tests where the test units are subjected to higher stress levels than the normal usage level so that information on the lifetime parameters can be obtained more quickly. Due to constrained resources in practice, stress durations must be determined carefully at the design stage in order to run an accelerated life test efficiently. These directly affect the experimental cost as well as the estimation precision of the parameters of interest. This article investigates these optimal decision variables based on two well-known optimality criteria under the constraint that the total experimental cost does not exceed a pre-specified budget. The optimal k-level constant-stress and step-stress accelerated life tests are compared for the Lomax failure data under Type-I censoring. Under the identical budget constraint, the efficiency of these two stress loading schemes is discussed based on the information matrix.
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