Which statement correctly differentiates MTBF and MTTF and their usage?

• A. MTBF is the mean time between failures for repairable systems; MTTF is the mean time to failure for non-repairable items; use MTBF when the item can be repaired, MTTF when the item is discarded after failure.
• B. MTBF equals the time to failure; MTTF equals time between failures.
• C. MTBF and MTTF are interchangeable and used identically.
• D. MTBF is the total time to failure; MTTF is the time to repair.

Answer: (A)