Comparing Sets of Data for 11+ Maths: A Parent's Guide
21 October 2026
Why comparing data matters
Comparing sets of data is a key skill in the 11+ maths exams. It helps children spot patterns, make decisions, and answer questions about information presented in tables or charts. Understanding how to compare data sets gives children confidence when tackling real exam questions.
What does it mean to compare data sets
When we compare data sets, we look at two or more groups of numbers to see how they are similar or different. This includes checking the average (mean), the middle value (median), the most common value (mode), and the spread (range) of each set.
Step 1: Find the mean
To find the mean, add up all the numbers in the dataset and divide by how many numbers there are. The mean tells you the average value, which is useful for comparing overall performance or results.
Step 2: Find the median
The median is the middle number when all the data is put in order from smallest to largest. If there is an even number of values, the median is the average of the two middle numbers. The median helps show the typical value in the set.
Step 3: Find the mode
The mode is the number that appears most often in the dataset. Sometimes there is no mode, or there can be more than one. The mode is useful for spotting the most common result or value.
Step 4: Find the range
The range is the difference between the largest and smallest numbers in the set. It shows how spread out the data is. A small range means the numbers are close together, while a large range shows more variation.
Worked example
Dataset A: 5, 8, 12, 15, 20 Dataset B: 7, 9, 11, 14, 18
Mean of A: (5 + 8 + 12 + 15 + 20) ÷ 5 = 60 ÷ 5 = 12
Mean of B: (7 + 9 + 11 + 14 + 18) ÷ 5 = 59 ÷ 5 = 11.8
Median of A: 12 (middle value) Median of B: 11 (middle value)
Mode of A: No mode (all numbers appear once)
Mode of B: No mode (all numbers appear once)
Range of A: 20 - 5 = 15 Range of B: 18 - 7 = 11
What can we learn from this example
Dataset A has a slightly higher mean and median than dataset B, but its range is larger. This means the values in dataset A are more spread out, while dataset B's values are closer together. Understanding these differences helps children answer data comparison questions accurately.
Key insight: Practising these steps with your child will build their confidence in comparing sets of data. Focus on calculating mean, median, mode and range, and talk about what these results show about each dataset.
