Which measure relates specifically to maintainability?

Mean Time to Repair (MTTR) is a crucial measure in assessing maintainability because it directly indicates the average time taken to repair a system or component after a failure. This measure provides insight into how quickly maintenance personnel can restore the system to operational status, which is a core aspect of maintainability.

A lower MTTR signifies that a system is easier and quicker to repair, which enhances its overall effectiveness and reliability in operation. In environments where downtime can be costly, understanding and improving MTTR is essential for maintaining high performance and operational availability.

Other options, while also related to system performance and reliability, focus on different aspects. Mean Time to Failure (MTTF) relates to the average time until a system or component fails and does not directly address how easily it can be repaired afterward. Mean Time Between Failure (MTBF) measures the average time between consecutive failures, which speaks to reliability but not to the maintenance aspect. Finally, Mean Time Between Maintenance Actions (MTBMA) pertains to the frequency of maintenance activities but does not specifically address the repair duration, which is the primary concern of maintainability.