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Quartiles

The median (Q₂) is the middle value of a set of data, which has been arranged in order.

The lower quartile (Q₁) is the median of the lower half of a set of data, once you have found the median.

The upper quartile (Q₃) is the median of the upper half of a set of data.

Example

The data below shows a sample of the percentages of pupils' test scores from Mr Brown's science class.

88 75 90 66 97 76 81

In order to find the median (Q₂) of this data, we need to put them in order first.

You need to find the Median (Q₂) first.

• Lower Quartile (Q₁) = 75
• Median (Q₂) = 81
• Upper Quartile (Q₃) = 90