Comparing sets of data for 11+ maths
21 October 2026
Comparing sets of data in 11+ maths
Comparing sets of data is a key skill in the 11+ CEM and GL maths exams. It helps children spot patterns and make sense of information presented in lists, tables or graphs.
Key insight: Comparing datasets helps children understand not just single numbers, but how whole groups of numbers relate to each other. This is a vital skill for data questions in the 11+.
What does comparing data mean
When we compare sets of data, we look for similarities and differences between groups of numbers. We use measures like the mean (average), median (middle value), mode (most common value), and range (spread between highest and lowest).
These measures help us see which group has higher or lower values, and which group is more consistent or varied.
Simple steps to compare data sets
First, list out the numbers in each set. Next, work out the mean, median, mode and range for each set. Compare these results to see how the sets differ.
If the mean or median is higher in one set, that group tends to have larger values. If the range is smaller, the group is more consistent.
Worked example: comparing two data sets
Set A = 3, 5, 7, 9, 11 Set B = 2, 4, 6, 8, 10
Step 1: Find the mean
Mean of Set A = (3 + 5 + 7 + 9 + 11) ÷ 5 = 35 ÷ 5 = 7
Mean of Set B = (2 + 4 + 6 + 8 + 10) ÷ 5 = 30 ÷ 5 = 6
Step 2: Find the median
Set A in order: 3, 5, 7, 9, 11. Median is 7 (middle value)
Set B in order: 2, 4, 6, 8, 10. Median is 6
Step 3: Find the mode
Set A: no repeated numbers, so no mode
Set B: no repeated numbers, so no mode
Step 4: Find the range Range of Set A = 11 - 3 = 8 Range of Set B = 10 - 2 = 8
Set A has a higher mean and median, but both sets have the same range. The correct answer is Set A tends to have higher values.
Helping your child practise
Encourage your child to compare data sets by working through examples like the one above. Ask them to explain each step and check their calculations. Using real-life data, such as scores or measurements, can make practice more engaging.
Regular practice with mean, median, mode and range will build confidence for the 11+ exam.
