# Simple and Weighted Arithmetic Mean

In mathematics and statistics, the arithmetic mean is the sum of a collection of numbers divided by the count of numbers in the collection.

## Simple arithmetic mean (or mean or average)

$$\bar{a}=\frac{a_{1}+a_{2}+...+a_{n}}{n}=\frac{1}{n} \times \sum_{i=1}^{n}a_{i}$$

where,

a1, ...— data set;
n— number of values.

## Weighted arithmetic mean

$$\bar{a}=\frac{a_{1}\times b_{1}+...+a_{n} \times b_{n}}{b_{1}+...+b_{n}}=\frac{\sum_{i=1}^{n}a_{i} \times b_{i}}{\sum_{i=1}^{n}b_{i}}$$

where,

b1, ...— non-negative weights.