the highest vertical 6. 5. In one of the examples in this chapter, we looked at the effect of electoral systems on the percentage of women in national legislatures, controlling for the level of cultural acceptance of women in leadership positions. In this exercise you will test a hypothesis that electoral systems affect turnout: In a comparison of countries, countries with PR systems will have higher turnouts than will countries that do not have PR systems. Level of economic development is an important control variable, because development, measured as gross domestic product (GDP) per capita, is known to be an alternative cause of voter participation. Therefore, evaluate the electoral system-turnout relationship, controlling for per capita GDP. 14 Among countries with low per capita GDP, the mean levels of turnout are as follows: non-PR countries, 56.1 percent; PR countries, 69.8 percent. For all low per capita GDP countries, 61.6 percent. Among countries with high GDP per capita: non-PR countries, 66.0 percent; PR countries, 68.5 percent. For all high per capita GDP countries, 67.4 percent. Among all countries, non-PR countries averaged 63.1 percent, and PR countries averaged 68.7 percent. The overall mean, for all countries: 66.0 percent. A. Construct a mean comparison control table from the information provided. (Numbers of cases are not provided, so the mean comparison control table will only display means.) B. Decide which pattern-spuriousness, additive, or interaction-best describes the set of relationships. Write a complete sentence explaining your answer. C. Draw a line chart of the electoral system- turnout relationship, controlling for per capita GDP. Enhance the readability of the chart by making 55 percent the lowest 164 THE ESSENTIALS OF POLITICAL ANALYSIS