# Quartile coefficient of dispersion

In statistics, the quartile coefficient of dispersion is a descriptive statistic which measures dispersion and which is used to make comparisons within and between data sets.

The statistic is easily computed using the first (Q1) and third (Q3) quartiles for each data set. The quartile coefficient of dispersion is:[1]

${\displaystyle {Q_{3}-Q_{1} \over Q_{3}+Q_{1}}.}$

Coefficient of variation also provide the similar data or facts.

## Example

Consider the following two data sets:

A = {2, 4, 6, 8, 10, 12, 14}
n = 7, range = 12, mean = 8, median = 8, Q1 = 4, Q3 = 12, quartile coefficient of dispersion = 0.5
B = {1.8, 2, 2.1, 2.4, 2.6, 2.9, 3}
n = 7, range = 1.2, mean = 2.4, median = 2.4, Q1 = 2, Q3 = 2.9, quartile coefficient of dispersion = 0.18

The quartile coefficient of dispersion of data set A is 2.7 times as great (0.5 / 0.18) as that of data set B.