Analysis of grouped and censored data from step-stress life test

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This paper studies statistical analysis of grouped and censored data obtained from a step-stress accelerated life test. We assume that the stress change times in the step-stress life test are fixed and the lifetimes observed are type I censored. Maximum likelihood estimates and asymptotic confidence intervals for model parameters are obtained. We provide an asymptotic statistical test for the cumulative exposure model based on the grouped and type I censored data. We also present the optimum test plan for a simple step-stress test when the lifetime under constant stress is assumed exponential. Finally we give an application of our methods by applying our analysis process to a real life data set. The proposed statistical methodology is especially useful when intermittent inspection is the only feasible way of checking the status of test units during a step-stress test.

Original languageEnglish
Pages (from-to)22-28
Number of pages7
JournalIEEE Transactions on Reliability
Issue number1
StatePublished - Mar 2004


  • Asymptotic variance
  • Confidence interval
  • Cumulative exposure model
  • Exponential distribution
  • Fisher information
  • Maximum likelihood
  • Optimum test plan


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