A Researcher Studying Support for International Institutions Finds That Democrats

Multiple Choice

A researcher studying support for international institutions finds that Democrats are more likely to support such institutions than are Republicans. When she controls for income, she finds that individuals with higher incomes are about 12 points more supportive of international institutions regardless of party. This is an example of a(n) ______.

A) additive effect
B) spurious effect
C) interactive effect
D) zero-order effect