Storks and a Water Tank
Across 17 European countries, the number of breeding stork pairs and the number of babies born each year rise and fall together. Their correlation is 0.62, too strong to be likely by chance.
Do storks bring babies?
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Science · Physical Science
Chapter 1: Measurement and the Nature of Science
A straight line through points is a claim, not a drawing.
Across 17 European countries, the number of breeding stork pairs and the number of babies born each year rise and fall together. Their correlation is 0.62, too strong to be likely by chance.
Do storks bring babies?
Make your guess to turn the page.
Still to come: 9 pages · Lab · Words to Know · What We Learned · 4 questions · Explain It in Writing · Open Questions
The idea this lesson is working on — Students read two quantities rising together as one causing the other. The book sets a graph whose cause is known, a tap filling a tank, against one whose cause is not, storks and births, and asks what made the difference. Ask: did anyone change one thing and hold the rest fixed? The idea to reach is that only an intervention separates causation from correlation.
Where the stork figure comes from — Robert Matthews, "Storks deliver babies (p = 0.008)", Teaching Statistics, 2000, used published figures for 17 European countries and found r = 0.62, written as a teaching example of a spurious correlation; land area is the obvious common cause. The independent variable conventionally goes on the horizontal axis so any reader can interpret the graph without asking.