Teach yer grandma to suck eggs. I've had to explain it to other several times, although I didn't bother getting into standard deviations and all that (wanted to keep it simple).low_grade wrote:And, probability works like this, think of coin tosses. Flip once, you get heads or tails, while the average is 0.5 in the long run, the first result is 0 or 1, very far off from 0.5. The more you flip, the closer you will get to 0.5.
Yup, I'm starting to think something like that is likely. The game does track total locomotive miles for oil, water and sand consumption, but it doesn't necessarily have to use total miles for breakdowns.So if breakdown chance is checked often, there shouldn't be the kind of variability I'm seeing. Your theory of one check per run, though it doesn't make sense to do it that way, actually makes perfect sense interpreting the results. Breakdown chance cannot be getting checked often. Then another random to determine where in the run it breaks down would explain everything.
I almost always use maintenance spurs, and it's not uncommon for a loco to crap itself between the station and the facilities, or between the two facilities for that matter. This can be when it is full of oil, and is also obviously when it is hauling no load at all. Then other locos with the same rating will haul full consists reliably for yonks. So yeah, checking per trip is probably how it works.
One way of checking for this, in rough terms anyway, would be to test locos doing a lot of short hops against locos doing long runs. If it is only checked per trip, the locos doing long runs should give lumpier data. If it is checked against actual mileage, there should be no difference.