Fisher–Tippett–Gnedenko theorem

The Fisher-Tippett-Gnedenko theorem is a mathematical theorem which says that if you take a bunch of numbers and you arrange them in order from smallest to biggest, then no matter how the numbers look, they will always form a particular shape if you plot them on a graph. This shape is called a "normal distribution" or a "bell curve." The middle of the bell curve is the average number and the bigger the curve is, the more numbers there are around the average number. This shape is useful when you are looking at a group of numbers that have been collected from a big group of people or things, because it will show you how many of the numbers fall around the average number, and also how many of them fall farther away from the average.