Abstract

A new concept of ageing distribution, namely new better (worse) than used in failure rate at specific time (NBUFR- (NWUFR- )) are introduced. The problem is investigated how to prove that after a specified time of operation the failure rate of an item is greater than the corresponding failure rate of a new item. This problem occurs in various areas like for instance in industry, when designing a maintenance policy. A test statistics that based on the goodness of fit method are derived for testing exponentially versus the NBUFR- alternatives. The percentiles and powers of this test statistic are tabulated. The asymptotic efficiencies for some alternatives are derived. A medical data is taken as a practical application.

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