The mean or average of a data set is one representation of the center of the data set. It is one measure of center. The others are the median and the mode. To calculate the mean, add all the data points together, then divide by the number of data points.

Suppose a data set represents the heights of different towers. The mean of this data set gives an idea of a typical height. Calculating the mean could be seen as rearragning the blocks so that all the towers have the same height.

After the blocks are rearranged, the towers each have a height of $4.$ Therefore, the mean is $4.$ If the heights are written as $x$, then the mean is sometimes written as $\bar{x}.$ The towers' mean height can then be written as $\bar{x}=4.$