Abstract: In view of the problem that the old approach of determining the sample size is too rough and the test sample size is too large, a reasonable application of the information entropy method is proposed to obtain the test data of the equipment system by fusing the prior information of each unit of the equipment system. The testability indices of the prior distribution are obtained, and the fault sample size and the test scheme are further determined by Bayes posterior risk criterion. The test data of an electric actuator system’s module are taken as an example and the failure detection rate is adopted as the test index. Compared with the traditional method, the failure sample quantity obtained by this method is reduced obviously through analysis and calculation, so the test cost is reduced. Meanwhile, the relative error of the test index is little, which guarantees the credibility. It is proved that the method reduces the test cost and guarantees the credibility.

Key words: fault sample size, testability test, posterior risk, prior information, Bayes method