Mean, median, mode and range explained (with examples)
TutorAura guide · Updated
The mean, median and mode are three kinds of average; the range measures how spread out the data is. To find them:
- Mean: add up the values and divide by how many there are.
- Median: put the values in order and find the middle one.
- Mode: the value that appears most often.
- Range: largest value minus smallest value.
Key takeaways
- Mean = total ÷ number of values.
- Median = middle value in order (average the two middle values for an even count).
- Mode = most common value; there can be none or several.
- Range = largest − smallest: a measure of spread.
Worked example
Test scores: 7, 3, 9, 7, 4, 10.
- In order: 3, 4, 7, 7, 9, 10 (6 values)
- Mean:
- Median: six values, so halfway between the 3rd and 4th:
- Mode: 7
- Range:
Check your own data with our mean, median and mode calculator.
Which average should you use?
| Average | Strength | Weakness | Use it for |
|---|---|---|---|
| Mean | Uses every value | Pulled by extreme values | Data without outliers |
| Median | Not affected by outliers | Ignores most values | Incomes, house prices, skewed data |
| Mode | Works for non-numbers | May not exist or may be several | Most popular size, colour, choice |
Comparing two data sets
Exam questions often ask you to compare two groups. Make two comparisons, one of an average and one of spread, and say what they mean in context:
"Class A had a higher median score (72 vs 65), so they generally did better. Class B had a smaller range (20 vs 35), so their scores were more consistent."
From a frequency table
For data in a frequency table, multiply each value by its frequency to find the total:
| Goals | Frequency | Goals × frequency |
|---|---|---|
| 0 | 3 | 0 |
| 1 | 5 | 5 |
| 2 | 2 | 4 |
Mean goals. The mode is 1 (highest frequency). With 10 values, the median is halfway between the 5th and 6th values, both 1, so it's 1.
Common mistakes
- Finding the median without ordering the values.
- Giving the frequency as the mode instead of the value.
- Dividing by the wrong count (the number of rows instead of the total frequency).
- Writing the range as "3 to 10" instead of one number.
Practice
For 5, 8, 2, 8, 6, 1, find the mean, median, mode and range. Answers: mean 5, median 5.5, mode 8, range 7. More in the averages and spread topic guide.
Estimating the mean from grouped data
When data are grouped into classes, you don't know the exact values, so you estimate the mean using the midpoint of each class:
| Height (cm) | Frequency | Midpoint | Midpoint × frequency |
|---|---|---|---|
| 4 | 5 | 20 | |
| 6 | 15 | 90 |
Estimated mean cm. It's an estimate because each value is assumed to sit at the middle of its class. For grouped data you give the modal class () rather than a single mode.
Frequently asked questions
How do I find a missing value when I know the mean?
Multiply the mean by the number of values to get the total, then subtract the values you know. If five numbers have a mean of 8, their total is 40; if four of them add to 31, the fifth is 9.
Can the mean be a decimal when all the data are whole numbers?
Yes. The mean number of children per family might be 2.4, even though no family has 2.4 children. Round sensibly for the context, or keep the decimal if the question asks for it.
What if a data set has two modes?
Then it is bimodal and you give both values. If every value appears the same number of times, there is no mode.
Sources
- National curriculum in England: mathematics programmes of study. Department for Education.
- Common Core State Standards for Mathematics. Common Core State Standards Initiative.
- Mathematics GCSE subject content and assessment objectives. Department for Education.
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