Confidence Intervals on MTTF and MTBF
The normal distribution is used to calculate confidence intervals on MTTF and MTBF. The calculations are similar to reliability/availability confidence calculations.
Let T i be the time to failures of the system in simulation run i. Therefore, mean and variance of these times, as well as the expected value of MTTF, are calculated as follows:
Where:
= The mean of the time to failure (T).Var(t) = The variance of the time to failure (T).
n = The total number of simulation runs.
The lower and upper confidence intervals of MTTF are found using the following formula:
Calculations for finding the confidence intervals on MTBF are similar to the MTTF confidence intervals calculations.