Editing Arithmetic mean (section)

===Weighted average===
{{main|Weighted average}}

A weighted average, or weighted mean, is an average in which some data points count more heavily than others in that they are given more weight in the calculation.<ref>{{Cite web|title=Mean {{!}} mathematics|url=https://www.britannica.com/science/mean|access-date=2020-08-21|website=Encyclopedia Britannica|language=en}}</ref> For example, the arithmetic mean of <math>3</math> and <math>5</math> is <math>\frac{3+5}{2}=4</math>, or equivalently <math>3 \cdot \frac{1}{2}+5 \cdot \frac{1}{2}=4</math>. In contrast, a ''weighted'' mean in which the first number receives, for example, twice as much weight as the second (perhaps because it is assumed to appear twice as often in the general population from which these numbers were sampled) would be calculated as <math>3 \cdot \frac{2}{3}+5 \cdot \frac{1}{3}=\frac{11}{3}</math>. Here the weights, which necessarily sum to one, are <math>\frac{2}{3}</math> and <math>\frac{1}{3}</math>, the former being twice the latter. The arithmetic mean (sometimes called the "unweighted average" or "equally weighted average") can be interpreted as a special case of a weighted average in which all weights are equal to the same number (<math>\frac{1}{2}</math> in the above example and <math>\frac{1}{n}</math> in a situation with <math>n</math> numbers being averaged).