Statistics

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.

Numbers 66, 75, 76, 81, 88, 90 and 97. 75 is labelled lower quartile, 81 is labelled media, and 90 is labelled upper quartile

You need to find the Median (Q2) first.

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