2019-02-15 MTBF / MTTR / 稼働率 MTBF (mean time between failure): 平均故障間隔 MTTR (mean time to repair): 平均修復時間 稼働率: MTBF / (MTBF + MTTF) http://officemiyajima.com/index.php?Miya_MTBF%2FMTTR