The Normal Distribution

Abstract

A symmetrical bell-shaped frequency distribution is often described as a normal distribution or a Gaussian distribution. It is known as the Gaussian distribution since it was derived by C. F. Gauss and included in his work about the theory of measurement of errors. The simple assumption of a normal distribution occurs only rarely for geological data. For example, if the density of an ore sample is measured ten times, then the results are usually distributed normally around the mean, presuming that there is no systematic error. On the other hand, there is no reason why the sample values from a mineral deposit should have a normal distribution (or any other simple, mathematically definable, distribution). It can, of course, be argued that the deposit is formed by definable physical-chemical and chemical processes and that therefore the grade distribution must also be mathematically definable. However, there are so many parameters involved, all of which can vary from location to location,, that it is just not possible to postulate a general conclusion about the frequency distributions of mineral deposits.