Normal Distribution - the Bell Curve

A distribution is a mathematical definition of how data is spread. One important type of distribution of continuous data is called the normal distribution. If you graph the data from a normal distribution, you will have what is commonly called a bell curve because of the shape.

The normal distribution is a very interesting one - it shows up in all kinds of natural phenomena. For example, if you measure the heights of a large number of adults and then graph the results, you will get a bell curve, the normal distribution.

There is really nothing "normal" about the bell curve, or abnormal about other continuous distributions. It is just a name, first used by several different mathematicians in about 1875. Like many words used in mathematics, normal distribution has a specific mathematical definition, but it does not mean the same as the word normal used in everyday English.

If you really want to impress someone, you can call the bell curve a Gausian distribution. Carl Freidrich Gauss, an important German mathematician and scientist, and Pierre Simon LaPlace, a French mathematician and astronomer, both claimed to have studied and used the normal distribution for analysis of errors before 1800.

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Last Updated: 8/2/2007
© K. A. Shearer 2007

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