Gallup. At its website (www.galluppoll.com) the Gallup Poll publishes results of a new survey each day. Scroll down to the end, and you’ll find a statement that includes an explanation such as this:

Results are based on telephone interviews with 1,008 national adults, aged 18 and older, conducted April 2–5, 2007. . . .

In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.

a) For this survey, identify the population of interest.

b) Gallup performs its surveys by phoning numbers generated at random by a computer program. What is the sampling frame?

c) What problems, if any, would you be concerned about in matching the sampling frame with the population?