**Mean**

The arithmetic mean is a number often used to describe the “average” value of a data set. The arithmetic mean is defined as:

mean = \dfrac{sum \,of\, the \,values}{number \,of \,values}

**Median**

The median is the “middle” value. To find the median, arrange the values in numerical order. If the number of values is odd, the median is the middle value. If the number of values is even, the median is the mean of the two middle values.

**Range**

The range is a number that describes the spread or dispersion of a data set. The range is the difference between the largest and smallest values.

range = (greatest value) – (least value)

## Example

Find the arithmetic mean, median and range.

(a) 6, 9, 11, 13, 18, 21

(b) 2, 45, 19, 3, 6