Question

the dommunity intervention trial for smoking cessation asked whether a community-wide advertising campaign would reduce smoking. the researchers located 11 pairs of communities that were similar in location, size, economic status, and so on. one community in each pair participated in the advertising campaign and the other did not. this is
a) an observational study
b) a matched pairs experiment
c) a completely randomized experiment
d) a block design
e) impossible to answer