Abstract: In the reliability assessment of electronic products, the history sample and the current sample often belong to different populations, which may have remarkable effect on the result of the assessment. In this article, the similarity degree between the history sample and the current sample is studied by similarity system analysisand denoted by an inheritance factor. The history posterior is obtained from the history sample and the innovation posterior is given by the noninformative prior. The two posteriors reflect the history information and the current test information respectively. The complex posterior is obtained from the history posterior and the innovation posterior via the inheritance factor, and statistical inference is made on the basis of the complex posterior. This method makes full use of the information of similar products and emphasizes the particular characteristics of the evaluated product.

Key words: exponential distribution, reliability assessment, Bayes method, similarity system analysis, inheritance factor