4 ms·
Small correction: Each year you have a (1-0.5^(1/100))≈0.69% chance of seeing a hundred year flood, if I'm not mistaken (and assuming hundred-year-floods happen
by mckirk 5y ago
Small correction: Each year you have a (1-0.5^(1/100))≈0.69% chance of seeing a hundred year flood, if I'm not mistaken (and assuming hundred-year-floods happen independently of each other).
At 1% chance each year, it would actually be 'sixtynine year floods'.
- phreeza 5y agoNo, if they arrive independently then they are best described by a poisson process, and the expected time to arrival is exactly 1/(event probability per interval). Not sure where you got the 0.5 from?
- mckirk 5y agoThe 0.5 derives from 'in a hundred year interval, there's a 50% chance to observe the event', which was my intuitive interpretation of a 'hundred year flood'. But as so often in statistics, that intuition was wrong -- 1/100 is indeed correct. (I'm at least not alone in that erroneous interpretation: "A common misunderstanding is that a 100-year flood is likely to occur only once in a 100-year period."[0]) The better way of looking at it is probably: In a 100*n year window, you expect to see n such events, which makes it pretty immediately obvious that the yearly incidence probability is 1/100. [0]: https://en.m.wikipedia.org/wiki/100-year_flood#Probability https://en.m.wikipedia.org/wiki/100-year_flood#Probability