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Chapter 1: Q 1.27. (page 15)
Explain why a census is often not the best way to obtain information about a population.
A Census of the entire population is time-consuming, costly, impractical, or sometimes impossible.
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Hepatitis B and Pancreatic Cancer.The article "Study Links Hepatitis B and Cancer of Pancreas" by D. Grady, appeared in the September 29, 2008 issue of the New York Times. It reported that, for the first time, a study showed that people with pancreatic cancer are more likely than those without the disease to have been infected with the hepatitis B virus. The study by M. Hassan et al . , titled "Association Between Hepatitis B Virus and Pancreatic Cancer" (Journal of Clinical Oncology, Vol. 26, No. 28, pp. 4557-4562) compared 476 people who had pancreatic cancer with 879 healthy control subjects. All were tested to see whether they had ever been infected with the viruses that cause hepatitis B or hepatitis C. The results were that no connection was found to hepatitis C, but the cancer patients were twice as likely as the healthy subjects to have had hepatitis B. The researchers noted, however, that "...while the study showed an association, it did not prove cause and effect. More work is needed to determine whether the virus really can cause pancreatic cancer." Explain the validity of the statement in quotes.
In Exercises 1.17-1.22, state whether the investigation in question is an observational study or a designed experiment. Justify your answer in each case.
Starting Salaries. The National Association of Colleges and Employers (NACE) compiles information on salary offers to new college graduates and publishes the results in Salary Survey.
Do you think that these rates are descriptive statistics or inferential statistics? Explain your answer.
Genocide. The document "American Attitudes about Genocide" provided highlights of a nationwide poll with 1000 participants. The survey, conducted by Penn Schoen Berland between June 30 and July 10, 2012, revealed that "66% of respondents believe that genocide is preventable."
(a). Is the statement in quotes an inferential or a descriptive statement? Explain your answer.
(b). Based on the same information, what if the statement had been "66% of Americans believe that genocide is preventable"?
Ballistic Fingerprinting. In an on-line press release, ABCNews.com reported that "...73 percent of Americans... favor a law that would require every gun sold in the United States to be test-fired first, so law enforcement would have its fingerprint in case it were ever used in a crime."
(a). Do you think that the statement in the press release is inferential or descriptive? Can you be sure?
(b). Actually, ABCNews.com conducted a telephone survey of a random national sample of 1032 adults and determined that 73% of them favored a law that would require every gun sold in the United States to be test-fired first, so law enforcement would have its fingerprint in case it were ever used in a crime. How would you rephrase the statement in the press release to make clear that it is a descriptive statement? an inferential statement?
The International 500. In Exercise 1.49 on page 16, you used simple random sampling to obtain a sample of 10 firms from Fortune Magazine's list of "The International 500."
(a) Use systematic random sampling to accomplish that same task.
(b) Which method is easier: simple random sampling or systematic random sampling?
(c) Does it seem reasonable to use systematic random sampling to obtain a representative sample? Explain your answer.
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