Data comparison practice: Comparing Sets of Data (CEM & GL)
21 October 2026
Comparing sets of data
Comparing sets of data is a key skill in 11+ maths. Children are often asked to look at two or more groups and decide how they are similar or different. This helps them understand and interpret information clearly.
Why it matters
Being able to compare sets of data is important for making good decisions. It helps children spot trends, find patterns, and answer questions about the information in tables, charts, or graphs.
Worked example
Imagine two classes record the number of books read in a month. Class A reads 12, 15, 14, 10 and 9 books. Class B reads 11, 13, 16, 12 and 8 books.
First, add up the total books for each class. For Class A: 12 + 15 + 14 + 10 + 9 = 60. For Class B: 11 + 13 + 16 + 12 + 8 = 60.
Next, find the average for each class. Divide the total by the number of pupils (5). For both classes: 60 ÷ 5 = 12.
Now, look at the range. For Class A: 15 - 9 = 6. For Class B: 16 - 8 = 8.
Both classes have the same average, but Class B has a wider range. This means the number of books read in Class B varies more than in Class A.
The correct answer is that both classes read the same total and average number of books, but Class B has a greater spread in the results.
Key insight: Comparing sets of data is not just about the totals or averages. Looking at the range and spread helps children see the full picture and answer questions with confidence.
Practical tips
Encourage your child to look at more than one feature when comparing data. Ask about totals, averages, highest and lowest values, and the range. This builds deeper understanding and helps avoid mistakes.
Building confidence
Regular practice with comparing data sets can make these questions feel much easier. Try looking at real-life examples, such as sports scores or family surveys, to bring the skill to life.
