In their study of influences on violent crime in Chicago neighborhoods, Robert Sampson, Stephen Raudenbush, and Felton Earls (1997, p. 919) hypothesized that efficacy would influence neighborhood crime rates. Collective efficacy was defined conceptually as a characteristic of the neighborhood: the extent to which residents were likely to help other residents and were trusted by other residents. To test this hypothesis, the researchers surveyed individuals from different neighborhoods. What is the unit of analysis in this study?

A. individuals
B. neighborhoods
C. crime rates
D. collective efficacy scores

B. neighborhoods