# Quartile coefficient of dispersion

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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 (*Q*_{1}) and third (*Q*_{3}) quartiles for each data set. The quartile coefficient of dispersion is:^{[1]}

## Example

Consider the following two data sets:

*A*= {2, 4, 6, 8, 10, 12, 14}

*n*= 7, range = 12, mean = 8, median = 8,*Q*_{1}= 4,*Q*_{3}= 12,**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,*Q*_{1}= 2,*Q*_{3}= 2.9,**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*.