Chapter 5 – Managing the Test Activities
Mean Time Between Failures (MTBF) – ISTQB Definition
Last Updated: July 12, 2026 · SoftwareTestPilot QA Team
Official ISTQB Definition
The arithmetic mean of the time between failures of a system, applicable to repairable systems.
In simple words
For a system that gets fixed, the average uptime between two failures.
Exam tip
MTBF is a core reliability KPI in operations dashboards.
Related terms
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