Through investigation,the authors figure that the average lifetime of the concrete dams in China is about 30-50 years.

In this paper a topologic analysis on the reliebility index system for power plant s protective devices is outlined, in it proposed a concept and algorithm on average life s corrent value to refrain from some weakness of the average life value.

This paper applys Bayes method and historic testing datas and the informations provived by industral technique to make Bayesian demostration test sampling plans of mean life θ=1/λ,thus decreasing working times.

Aiming at the problem how to determine whether the samples are IID, this paper analyzes the test of IID samples and discusses the statistic analysis of reliability under IID and non-IID conditions by taking the mean life for example.

This paper gives an assessment method for the mean life of complex system based on component test information.

In this paper,a new approach which combines the least-square method with Bayes theorem,takes advantage of the parameter estimation for single Weibull distribution was developed to estimate the mean time to failure and the reliability estimation of the mixed Weibull population.

The estimation of the median lifetime and the mean time to failure and the confidence limits of the mean time to failure of electrical products were given.

In the theory research and application work of the reliability, we wish to find the accuratecalculating formula about the mean time to failure of the products easily.