# Mean

## The Mean of a Data Set

The mean of a set of numbers, sometimes simply called the average , is the sum of the data divided by the total number of data.

Example :

Find the mean of the set $\left\{2,5,5,6,8,8,9,11\right\}$ .

There are $8$ numbers in the set. Add them all, and then divide by $8$ .

$\begin{array}{l}\frac{2\text{\hspace{0.17em}}+\text{\hspace{0.17em}}5\text{\hspace{0.17em}}+\text{\hspace{0.17em}}5\text{\hspace{0.17em}}+\text{\hspace{0.17em}}6\text{\hspace{0.17em}}+\text{\hspace{0.17em}}8\text{\hspace{0.17em}}+\text{\hspace{0.17em}}8\text{\hspace{0.17em}}+\text{\hspace{0.17em}}9\text{\hspace{0.17em}}+\text{\hspace{0.17em}}11}{8}=\frac{54}{8}\\ =6.75\end{array}$

So, the mean is $6.75$ .