In a probability sampling procedure, all individuals in a population have an equal probability of being selected

How does Knowledge Networks ensure participation in its Web-based surveys?

a. Respondents are paid a small sum every time they participate. b. Respondents are selected from the cell-phone-only segment of the population. c. Respondents are randomly sampled. d. Respondents must own their own computer.

Term limits for members of the U.S. Congress can be imposed only by __________

a. state legislatures b. congressional legislation c. a public referendum d. constitutional amendment