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Chapter 1: Q 1.6. (page 7)
Fill in the following blank:
Observational studies can reveal only association, whereas experiments can help establish .
Observational studies can reveal only association, whereas experiments can help establish causation.
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In Exercises 1.92-1.97, we present descriptions of designed experiments. In each case, identify the
(a) experimental units
(b) response variable
(c) factor (s)
(d) levels of each factor:-
(e) treatments.
Highway Signs. A driver's ability to detect highway signs is an important consideration in highway safety. In his dissertation, High way Construction Safety and the Aging Driver, S. Younes investigated the distance at which drivers can first detect highway caution signs. This distance is called the detection distance. Younes analyzed the effect that sign size and sign material have on detection distance. Drivers were randomly assigned to one combination of sign size ( small, medium, and large ), and sign material ( 1, 2, and 3 ). Each driver covered the same stretch of highway at a constant speed during the same time of day, and the detection distance, in feet, was determined for the driver's assigned caution sign.
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.
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.
Heart Failure. In the paper "Cardiac-Resynchronization Therapy with or without an Implantable Defibrillator in Advanced Chronic Heart Failure" (New England Journal of Medicine, Vol. 350, pp. 2140-2150), M. Bristow et al. reported the results of a study of methods for treating patients who had advanced heart failure due to ischemic or nonischemic cardiomyopathies. A total of 1520 patients were randomly assigned in a 1:2:2 ratio to receive optimal pharmacologic therapy alone or in combination with either a pacemaker or a pacemaker-defibrillator combination. The patients were then observed until they died or were hospitalized for any cause.
Oklahoma State Officials. The five top Oklahoma state officials are displayed in Table 1.2 on page 11. Use that table to solve the following problems.
(a). List the 10 possible samples (without replacement) of size 3 that can be obtained from the population of five officials.
(b). If a simple random sampling procedure is used to obtain a sample of three officials, what are the chances that it is the first sample on your list in part (a)? the second sample? the tenth sample?
The members of a population are numbered 1-4.
(a). List the 6 possible samples (without replacement) of size 2 from this population.
(b). If an SRS of size 2 is taken from the population, what are the chances of selecting 2 and 3? Explain your answer.
(c). Use Table I in Appendix A to obtain an SRS of size 2 from the population. Start at the single-digit number in line number 17 and column number 7, read down the column, up the next, and so on.
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