When two maps match, you may describe the match, but you may not claim cause without more evidence. This lesson shows the wording and the check that keeps you safe.
It belongs to map and graph skills. A related field version appears in distinguishing correlation from a proven cause in a field dataset.
How do I describe a match between two maps?
Name the pattern on each map, then say where they coincide. Finish with what the match does not show.
A safe frame is: “Districts with [high value on map A] also tend to have [high value on map B], but the maps do not show that one causes the other.”
Worked example: stalls and litter
This is a worked example. Two maps of four fictional districts show food stalls per km² (Map A) and pieces of litter per km² (Map B). A table supplies population density as well.
| District | Stalls per km² | Litter per km² | People per km² |
|---|---|---|---|
| D1 | 40 | 300 | 4 000 |
| D3 | 8 | 60 | 800 |
| D4 | 52 | 410 | 5 200 |
| D6 | 3 | 25 | 300 |
The two maps match: the districts with more stalls have more litter. A student who says “stalls cause litter” has gone beyond the maps.
Check for a third factor. Divide litter by people (per 1 000 people).
- D1: 300 ÷ 4 = 75.
- D3: 60 ÷ 0.8 = 75.
- D4: 410 ÷ 5.2 is about 79.
- D6: 25 ÷ 0.3 is about 83.
The litter for each 1 000 residents is 75 to 83 in every district. Population density therefore tracks both maps closely, so it is a likely third factor.
Safe conclusion. “High stall density is associated with high litter density in these four districts. Both also rise with population density, so the maps do not show that stalls cause litter.”
The mistake: writing cause from a match
A typical slip is: “Food stalls cause litter, so the council should close stalls.” The maps give a match, not a mechanism.
| Weak sentence | Careful sentence |
|---|---|
| “Stalls cause litter.” | “Stall density coincides with litter density.” |
| “More stalls means more litter.” | “Districts with more stalls also have more litter, and more people.” |
| “Close the stalls.” | “Further evidence, such as litter per person, is needed before a cause is claimed.” |
Check yourself
Two maps show ice cream sales and swimming pool visits both highest in the same coastal districts. A student writes “ice cream causes people to go swimming”. Give one careful rewrite and one third factor.
Answer
A careful rewrite: “Districts with high ice cream sales also have high swimming pool visits, but the maps do not show that one causes the other.”
A possible third factor is hot weather, because it may raise both. The maps do not include temperature, so this is an idea to check, not a fact.
What to study next
Practise choosing the right graph for such data in choosing a graph for geographical data. Then test yourself with the map and graph skills practice.
The graph evidence and fair-comparison lab offers more fair-comparison drills. For a teacher to review your wording, see online one-to-one Geography tuition.