In statistics, a normal distribution is an ideal distribution which is symmetrical about its mean. It can be written in the form:
where f(x) is the relative frequency, σ is the standard deviation, μ is the mean, and π and e have their usual values. Note that in a normal distribution the mean, median, and mode coincide. The characteristic bell-shaped curve shown when f(x) is plotted against x is called the normal curve. The distribution is also known as the "Gaussian distribution" for Karl Gauss.