More math, more income? Is there a relationship
between a country's per capita income and its
students' achievement in mathematics? Here is a
scatterplot of per-capita gross domestic product
versus average score on an international mathe-
matics achievement test for 26 countries in Europe
and Asia. 30
Math achievement
600
550
500
450-
400
O
10,000
20,000 30,000 40,000 50,000
GDP per capita
(a) Interpret the value r = 0.59.
(b)
Will increasing per-capita income in a country
cause higher student achievement in mathematics?
Explain your reasoning.