Which metric describes the average time required to repair a failed component?

Which metric describes the average time required to repair a failed component?

• A. MTBF
• B. MTTR
• C. MTTF
• D. Availability

Answer: (B)

Mean Time To Repair (MTTR) describes the average time it takes to repair a failed component. It captures the duration from failure detection through diagnosis, replacement or repair, and testing until the system is back online. This directly answers “how long does it take to fix something on average,” which is why it’s the best fit for the question. MTBF, in contrast, is the average time the system runs before a failure occurs, not the repair time. MTTF is used for non-repairable items and represents the time to first failure. Availability is a broader measure of how often the system is up, typically derived from MTBF and MTTR as uptime over total time, so it’s not the direct metric for repair duration itself.

Mean Time To Repair (MTTR) describes the average time it takes to repair a failed component. It captures the duration from failure detection through diagnosis, replacement or repair, and testing until the system is back online. This directly answers “how long does it take to fix something on average,” which is why it’s the best fit for the question.

MTBF, in contrast, is the average time the system runs before a failure occurs, not the repair time. MTTF is used for non-repairable items and represents the time to first failure. Availability is a broader measure of how often the system is up, typically derived from MTBF and MTTR as uptime over total time, so it’s not the direct metric for repair duration itself.