The interquartile range (IQR) is a way to measure how spread out the middle half of a set of numbers is.
To find the IQR, you first need to arrange all the numbers in order. Then you identify the lower quartile (Q1), which is the value at the first quarter of your data set, and the upper quartile (Q3), which is the value at the third quarter. The IQR is the difference between Q3 and Q1.
This range helps you understand how much the middle values of your data vary, and is useful for spotting any unusually high or low numbers, known as outliers.
Examiner-written GCSE Maths revision resources that improve your grades 2x
- Written by expert teachers and examiners
- Aligned to exam specifications
- Everything you need to know, and nothing you don’t
Share this article
written revision resources that improve your