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A Survey of 100,000 Physicians. In 2010 , the Physicians Foundation conducted a survey of physicians' attitude about health care reform, calling the report "a survey of 100,000 physicians." The survey was sent to 100,000 randomly selected physicians practicing in the United States: 40,000 via postoffice mail and 60,000 via email. A total of 2,379 completed surveys were received. 11 (a) State carefully what population is sampled in this survey and what is the sample size. Could you draw conclusions from this study about all physicians practicing in the United States? (b) What is the rate of nonresponse for this survey? How might this affect the credibility of the survey results? (c) Why is it misleading to call the report "a survey of 100,000 physicians"?

An opinion poll calls 2000 randomly chosen residential telephone numbers in Portland and asks to speak with an adult member of the household. The interviewer asks, "How many movies have you watched in a movie theater in the past 12 months?" In all, 831 people respond. The sample in this study is (a) all adults living in Portland. (b) the 2000 residential phone numbers called. (c) the 831 people who responded.