Current Articles | Archives ReliabilityStaff posted on October 23, 2006 | Reliability Suppose that the failure of a unit in a system occurs after time T, and that it has the probability density function f(t). The failure distribution function is the probability of an item failing in the time interval: The reliability function is the probability of a unit that does not fail in the same time interval. Mean Time To Failure (MTTF) is defined as: The Mean Time Between Failure (MTBF) is approximately the same as MTTF if the past in a system can be replaced and the time required to do so is very short compared to the MTTF. If the repair is time consuming and has to be taken into consideration, then: MTBF = MTTF + MTTR Please enable JavaScript to view the comments powered by Disqus.