Comparing sets of data made simple
21 October 2026
Comparing sets of data made simple
Comparing sets of data is a key skill in 11+ maths, especially for CEM and GL style questions. Children need to look at two or more groups and decide how they are similar or different. This often involves comparing averages (mean or median) and the spread (range) of the data.
How to approach data comparison
Start by looking at the main features of each set. Check the average score or value for each group, then see how spread out the results are. Sometimes, you may also need to look for the highest and lowest values.
Worked example
Suppose Group A has test scores: 6, 7, 8, 9, 10
Group B has test scores: 5, 7, 8, 11, 12
Step 1: Work out the mean for each group.
Group A mean: (6 + 7 + 8 + 9 + 10) ÷ 5 = 40 ÷ 5 = 8
Group B mean: (5 + 7 + 8 + 11 + 12) ÷ 5 = 43 ÷ 5 = 8.6
Step 2: Find the range for each group.
Group A range: 10 - 6 = 4
Group B range: 12 - 5 = 7
Step 3: Compare the results.
Group B has a slightly higher mean score (8.6 vs 8), but also a wider range (7 vs 4).
The correct answer is: Group B did better on average, but Group A's scores were more consistent.
What does this tell us
When comparing sets of data, it is not just about which group has the highest average. It is also important to notice how spread out the scores are. A smaller range means the results are more consistent.
Key insight:
In 11+ maths, always compare both the average and the range. This gives a clearer picture of how each group performed, helping your child answer data questions with confidence.
