Economics, 3rd Edition

The Stork Population and New 

Born Babies in Region X

The scatter plot of the information in 

the Table shows the stork population 

over a period of time in Region X and 

the number of new born babies over the 

same time period.

Th

S

t k P

l ti

FIGURE 2A.4

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Stork population (vertical axis) against new

babies born (horizontal axis)

Looking at the scatter plot in Figure 2A.4 it seems clear that there is a correlation between the two 

variables and one might be drawn to the conclusion that storks do indeed bring babies. However, common 

sense and biology tell us that what we are seeing is simply a coincidence – two variables which seem to 

have some correlation but where the correlation is due to chance. To determine whether there is a relation-

ship between variables and the extent to which any relationship is due to chance can be identified by the 

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CHAPTER 2  THINKING LIKE AN ECONOMIST  35

use of different statistical tests. If the appropriate tests were carried out on this data it is likely to tell us that 

there is a significant correlation and the extent to which the correlation is due to chance. This example serves 

as another reminder that economists must always question and never simply accept things at face value.