Normal distribution says that the probability of observing a particular data value is greatest near the mean value—the average—and dies away rapidly as the difference from the mean increases. This formula defines a special family of bell-shaped probability distributions, often good models of everyday real-world observations. Normal distribution led to the concept of the ‘average man,’ tests of the significance of experimental results, such as medical trials, and an unfortunate tendency to default to the bell curve as if nothing else existed.

## The Formula to Get 42 Billion Digits of π

While writing "7 Utterly Well-written Math Books About Pi," I found a very interesting math formula that will give you 42 consecutive digits of π accurately but is still wrong.