Is Mean Time to Failure (MTTF) Equal to Mean Time of Life for Unrepairable Systems?

Abstract One of the most important reliability parameters is mean time to failure (MTTF). It widely accepted that MTTF equal life E T . This article shows this not necessarily true. Although for commonly used statistical distributions (such as exponential, Gaussian, chi-square, Fisher-Tippett distributions) values and are equal, case log-normal distribution. Similarity, some less Breit-Wigner distribution) may also require calculation adjustments resulting from ≠ Ignoring discrepancy, an erroneous value can be obtained.