_____ involves an interest group's rank-and-file membership as well as outreach to ordinary people outside the organization

When researchers contact a single participant who leads them to other participants who, in turn, lead to even more participants, the researchers are using

a. cluster sampling. b. purposive sampling. c. systematic sampling. d. chain-referral sampling.

Economic interest groups include all of the following except

a. agricultural groups. b. labor groups. c. local government groups. d. education groups. e. All of the above are types of economic interest groups.