MTTD would be the difference between the onset of any event that is deemed revenue impacting and its actual detection by the technician who then initiates some specific action to recover the event back to its original state. This would not be the same as starting the “Mean Time To Repair” (MTTR) clock. (i.e. once the technician receives a trouble ticket). The onset of any revenue impacting event almost always is recorded at some specific time by some specific equipment. The key element would be to bring the detection tool into the technician’s environment and then measure the difference between the events time stamp and the tech’s first action indicating recognition of the event (MTTD).
From this value a “detection skill ratio” could be calculated by dividing the MTTR by MTTD
Detection Skill = Mean Time to Repair / Mean Time to Discovery
DS = MTTR/MTTD