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Chapter 1: Q 1.34. (page 15)
Identify two methods for obtaining a simple random sample.
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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.
Dental Hygiene: Which Toothbrush? In an experiment reported by J. Singer and D. Andrade in the article " Regression Models for the Analysis of Pretest / Posttest Data " ( Biometrics, Vol . 53, pp . 729-735 ), the effect of using either a conventional or experimental ( hugger ) toothbrush was investigated. Twelve female and 12 male preschoolers were selected. Within each gender group, six were randomly assigned to the conventional toothbrush and the remaining six to the experimental toothbrush. After each subject brushed with the assigned toothbrush, a dental plaque index was measured. The higher the dental plaque index, the greater was the amount of plaque on an individual's teeth.
(a) Is the statistical design described here a completely randomized design or a randomized block design? Explain your answer.
(b) If the statistical design is a randomized block design, what are the blocks?
Ideally, in stratified sampling, the members of each stratum should be relative to the characteristic under consideration.
Which of the following sampling procedures involve the use of probability sampling?
a . A college student is hired to interview a sample of voters in her town. She stays on campus and interviews 100 students in the cafeteria.
b . A pollster wants to interview 20 gas station managers in Balti more. He posts a list of all such managers on his wall, closes his eyes, and tosses a dart at the list 20 times. He interviews the people whose names the dart hits
Medical Testing on Animals. In its Summer 2013 Animal Action Report, the National Anti-Vivisection Society stated that "59% of Americans between the ages of 18 and 29 oppose medical testing on animals." The percentage of 59% was computed from sample data.
(a). Identify the population under consideration.
(b). Identify the sample under consideration.
(c). Is the statement in quotes descriptive or inferential?
(d). If you wanted to make it clear that the percentage of 59% was computed from sample data, how would you rephrase the statement in quotes?
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