One example is the number
One example is the number of births in a city in a given week, and another is the number of cosmic rays detected in a given area in a day. It justifies the rule of thumb that, if you count N events, the uncertainty in the number is given by the square root of N. Also called the "law of small numbers," it says the probability that an event occurs N times is given by e to the minus x, times x to the N, divided by N factorial, where x is the expected number of events. Radioactive decay counting is one place where it is commonly found. For 10 points, what is this statistical distribution discovered by a 19th- century French mathematician?
One example is the number of births in a city in a given week, and another is the number of cosmic rays detected in a given area in a day.
{Poisson} distribution