Edexcel International GCSE Mathematics A · 4MA1
Mean, median and mode
Averages summarise a typical value in different ways. The mean uses all observations and is sensitive to outliers. The median uses the middle position after sorting. The mode identifies the most frequent value and may not be unique.
Key method
Mean = total/number of values. Sort before finding the median; with an even count, average the two middle values. Always compare spread as well as centre when evaluating data sets.
Worked example
Find the mean, median and mode of 2, 3, 3, 4, 18.
- The total is 30 across five observations, giving mean 6.
- The data are ordered; the third observation is 3.
- The value 3 appears twice, more often than any other value.
Answer and interpretation
Mean 6, median 3, mode 3. The high value 18 pulls the mean upward.
Common mistake
Choosing the middle value from an unsorted list does not find the median.
Practise independently
Four values have mean 7. A fifth value of 12 is added. Find the new mean.
Check your answer
The new total is 4 × 7 + 12 = 40, so the mean is 8.
Syllabus connection
This lesson develops mean, median and mode within the statistics area. Start with the worked method, attempt the independent question without looking at its answer, then explain any correction in your own words. Check the official specification for your tier’s full requirements.
Related resources
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