RocketDigitsStart free

All skills › Year 10 › Statistics & Probability

Year 10 · Statistics & Probability

Quartiles and interquartile range

Quartiles split ordered data into quarters. The interquartile range (IQR) measures spread; standard deviation measures spread around the mean.

Try a question

Loading a question…

How to do it

  1. Order the data. The median splits it in two.
  2. Q1 is the median of the lower half, Q3 of the upper half.
  3. IQR = Q3 − Q1.

Worked example

IQR of 1, 3, 4, 6, 8, 9, 12
Median 6. Lower half 1, 3, 4: Q1 = 3. Upper half 8, 9, 12: Q3 = 9
IQR = 9 − 3 = 6

With a free account, these play as step-by-step animations.

Watch out
Order the data first, every time.

Practise Quartiles and interquartile range properly

Ten-question rounds with instant marking, a lesson under every question, stars and badges. Free to start, and the first week includes Premium.

Create a free account

More Statistics & Probability skills