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Chapter 1: Q 1.41. (page 16)
Estimating Median Income. Explain why a sample of 30 dentists from Seattle taken to estimate the median income of all Seattle residents is not representative.
The dentists belong to a high-income group whose earnings aren't reflective of the overall population's earnings.
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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.
Aspirin and Cardiovascular Disease. In the article by P. Ridker et al. titled "A Randomized of Low-dose Aspirin in the Primary Prevention of Cardiovascular Disease in Women" (New England Journal of Medicine, Vol. 352, pp. 1293鈥�1304), the researchers noted that "We randomly assigned 39,876 initially healthy women 45 years of age or older to receive 100 mg of aspirin or placebo on alternate days and then monitored them for 10 years for a first major cardiovascular event (i.e., nonfatal myocardial infarction, non-fatal stroke, death from cardiovascular causes)."
Sampling Dorm Residents. Students in the dormitories of a university in the state of New York live in clusters of four double rooms, called suites. There are 48 suites, with eight students per suite.
(a) Describe a cluster sampling procedure for obtaining a sample of 24 dormitory residents.
(b) Students typically choose friends from their classes as suitemates. With that in mind, do you think cluster sampling is a good procedure for obtaining a representative sample of dormitory residents? Explain your answer.
(c) The university housing office has separate lists of dormitory residents by class level. The number of dormitory residents in each class level is as follows. Use the table to design a procedure for obtaining a stratified sample ( with proportional allocation ) of 24 dormitory residents.
Provide a scenario of your own in which a sample is not representative.
Persistent Poverty and IQ. An article appearing in an issue of the Arizona Republic reported on a study conducted by G. Duncan of the University of Michigan. According to the report, "Persistent poverty during the first 5 years of life leaves children with IQs 9.1 points lower at age 5 than children who suffer no poverty during that period...." Is this statistical study an observational study or is it a designed experiment? Explain your answer.
Regarding observational studies and designed experiments:
(a) Describe each type of statistical study.
(b) With respect to possible conclusions, what important difference exists between these two types of statistical studies?
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