How to Calculate the Mean

Calculates the mean of a data set as the sum ÷ the count. List the values on one line, separated by commas or spaces.

Explanation

The mean is the most common way to summarise a set of numbers with a single value: add everything up and divide by how many values there are.

\bar{x} = \dfrac{x_1 + x_2 + \cdots + x_n}{n} = \dfrac{1}{n}\sum_{i=1}^{n} x_i

Here $x_i$ is the $i$ -th value, $n$ is the number of values, and $\bar{x}$ ("x-bar") is the mean.

Example

For the data 12, 15, 18, 20, 25 the sum is $12 + 15 + 18 + 20 + 25 = 90$ and the count is 5.

\bar{x} = \dfrac{90}{5} = 18

Watch out

The mean is pulled towards extreme values. A single billionaire in a list of salaries drags the average far above what most people actually earn.

When that happens the median, the middle value, describes the data better. A large gap between the mean and the median is a sign that the distribution is skewed, so it is worth calculating both.