7	Patterns of chance Normal Distribution

What does it say?

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. How rapidly depends on a quantity called the standard deviation.

Why is that important?

It defines a special family of bell-shaped probability distributions, which are often good models of common real-world observations.

What did it lead 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.