# The Arithmetic Mean The arithmetic mean of two numbers $a$ and $b$ (where $a \le b$) is a number $m$ such that $ m-a = b-m $ In other words, the arithmetic mean of two numbers is a number that is located exactly in-between the two numbers in an [[Arithmetic Sequence]]. The arithmetic mean can be used as a measure of central tendency of a population, in which case is calculated by dividing the sum of all elements by the number of elements. It is commonly known as the average. $ m = \frac{1}{n} \sum_{i=1}^n x_i $ The arithmetic mean is similar to the [[The Geometric Mean]], although the arithmetic is much more widely used in statistics and probability.