Range

A measure of spread for a distribution of a numerical variable that is calculated as the difference between the largest and smallest values in the distribution.

The range is less useful than other measures of spread because it is strongly influenced by the presence of just one unusually large or small value; hence, the range conveys only one aspect of the spread of the distribution. It is recommended that a graph of the distribution is used to check the appropriateness of the range as a measure of spread and to emphasise its meaning as a feature of the distribution.

Example

The maximum temperatures, in degrees Celsius (°C), in Rolleston for the first 10 days in November 2008 were: 18.6, 19.9, 20.6, 19.4, 17.8, 18.1, 17.8, 18.7, 19.6, and 18.8.

The largest value is 20.6°C and the smallest is 17.8°C.

The range of the maximum temperatures over these 10 days is 20.6°C – 17.8°C = 2.8°C

The data and the range are displayed on the dot plot below.

See: measure of spread

Curriculum achievement objectives references

Statistical investigation: Levels 5, 6, 7, 8