Mean, median and range in geography
Which number best describes your fieldwork results?
The mean uses every value. The median is the middle value. The range shows the gap between the largest and smallest values.
Choose a useful summary
A quadrat is a square frame used to mark a sampling area. The mean is useful when you want to include every observation. A very large or small value pulls it towards that value. The median is less affected by an extreme result.
Keep the spread
Two places can have the same mean but very different results. Give the range as well when the spread helps answer your question.
Worked example
| Litter items in equal-sized quadrats |
|---|
| 2 · 3 · 3 · 4 · 18 |
- Total = 2 + 3 + 3 + 4 + 18 = 30. Mean = 30 ÷ 5 = 6 items per quadrat.
- The values are in order. The middle value is 3, so the median is 3 items.
- Range = 18 − 2 = 16 items. The mean of 6 is higher than four of the five counts because of the count of 18.
With an even number of values, the median is the mean of the two middle values. Do not remove an unusual result just because it is inconvenient; first check how it was collected.
Check you’ve got it
Which summary changes least if 18 becomes 28?
Check your answer
The median stays 3. The mean rises to 8 and the range rises to 26.
Try it yourself
Use this new resource. Check your answers, then try another set.
Mean, median and range
Each observation uses the same area. One count is much higher than the others; keep it in the calculations.
| Site | Litter items in a 10 m² quadrat |
|---|---|
| Site 1 | 44 |
| Site 2 | 17 |
| Site 3 | 18 |
| Site 4 | 21 |
| Site 5 | 17 |
Resource description
Fictional field observations
Your course and question context
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Interquartile range in geography → · Choose a skills workout