What does MTBF stand for?

• A. Mean Time To Repair
• B. Mean Time Between Failures
• C. Maximum Time Before Failure
• D. Mean Time Before Failure

Answer: (B)

MTBF stands for Mean Time Between Failures. It’s a reliability measure for repairable systems that indicates the average amount of operating time you can expect between successive failures. This helps with planning maintenance, inventory, and predicting how often a machine will fail in service. It’s the time the system runs before a failure occurs, not counting the repair time. The longer the MTBF, the less frequently failures happen. After a failure is repaired, the next interval begins. This is different from Mean Time To Failure (used for non-repairable items) and from Mean Time To Repair (the downtime required to fix a failure). In practice, availability is often estimated as MTBF divided by MTBF plus MTTR.