A team of researchers is studying the effect of inequality in metropolitan areas on aggregate levels of trust. The researchers define inequality as differences in access to resources between groups of people in the area. This variable is measured by an index of inequality for each metropolitan area, ranging from 0 (no difference in access to resources between groups) to 100 (some groups have access, and others have none). The other variable is average level of trust in metropolitan areas.

a. What is the independent variable in this study?

b. What is the dependent variable?

c. What is the unit of analysis?

d. What is the sampling strategy?