surely the likelihood of getting a wrong number from a building that you know
has to be statistically smaller than all the other buildings in the world.

never mind the fact that nobody is in a non-boarding school at 5am...
( rachelswipe with a fork, Mon 9 Dec 2013, 15:01, 2 replies, latest was 11 years ago)

The odds go up dramatically if there is a ghost mum roaming the corridors though

( tangledupinblue hairy badge with moving eyes, Mon 9 Dec 2013, 15:04, Reply)

Erm, no. Not in the slightest.
OK, I'm not being patronising here, I swear, because this part of probability tends to confuse a lot of people, but the subset of phone numbers or buildings you do know (very small) vs the subset of phone numbers of buildings you don't (very large) has no bearing at all on those phone numbers calling you. It's just statistically irrelevant, assuming you assume that the call isn't meant for you. It simply comes down to the number, and each number has an equal chance of calling you. Same as each lottery ball has an equal chance of being drawn.

If the call WAS for you, of course, then the opposite of what you think is actually true, it's much more likely to come from a number of a building you do know, but that's not a straight probability question.
( the mighty badger Aphrodite, on a bar stool, by your side, Mon 9 Dec 2013, 15:11, Reply)