arithmetic mean
sum of a collection of numbers divided by the number of numbers in the collection
expectation
long-run average value of a random variable
mean time to repair
measure of the maintainability of repairable items; average time required to repair a failed component or device
mean time to recovery
measure of the maintainability of repairable items; average time from discovery of a failure to completion of repairs
mean down time
average time that a system is unavailable
mid-range
statistic which can be calculated as the arithmetic mean of the maximum and minimum values of any sample