Actually, the important odds are: given that you've met a 75-year old explosives professional, how likely is it that he was skilful instead of lucky? To get a

Actually, the important odds are: given that you've met a 75-year old explosives professional, how likely is it that he was skilful instead of lucky? To get a good estimate of this you need to come up with some priors about how many skilful and unskillful equivalents there were at the age of 30 and how much worse the unskillful ones are at staying alive.