Chapter 8 hw stats - Ch 08 HW Your response has been submitted successfully Points Awarded 8 Points Missed 13 Percentage 38 1 How can we reduce the

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Ch. 08 HW Your response has been submitted successfully. Points Awarded 8 Points Missed 13 Percentage 38% 1. How can we reduce the rate of refusals in telephone surveys? Most people who answer at all listen to the interviewer's introductory remarks and then decide whether to continue. One study made telephone calls to randomly selected households to ask opinions about the next election. In some calls, the interviewer gave her name, in others she identified the university she was representing, and in still others she identified both herself and the university. The study recorded what percent of each group of interviews was completed. Select the correct option from the drop-down list. The study presented to you is: This is an experiment because we assume that the treatment is selected randomly by the interviewer. Points Earned:0/1 Correct Answer: An experiment Your Response: An observational study 2. How can we reduce the rate of refusals in telephone surveys? Most people who answer at all listen to the interviewer's introductory remarks and then decide whether to continue. One study made telephone calls to randomly selected households to ask opinions about the next election. In some calls, the interviewer gave her name, in others she identified the university she was representing, and in still others she identified both herself and the university. The study recorded what percent of each group of interviews was completed. True or false: The explanatory variable is the level of identification, and the response variable is whether or not the interview is completed. In this study, the explanatory variable is the level of identification and the response variable is whether or not the interview is completed. Points Earned:1/1 Correct Answer: True Your Response: True Observational studies had suggested that vitamin E reduces the risk of heart disease. Careful experiments, however, showed that vitamin E has no effect. According to a commentary in the Journal of the American Medical Association: Thus, vitamin E enters the category of therapies that were promising in epidemiologic and observational studies but failed to deliver in adequately powered randomized controlled trials. As in other studies, the "healthy user" bias must be considered, i.e., the healthy lifestyle behaviors that characterize individuals who care enough about their health to take various supplements are actually responsible for the better health, but this is minimized with the rigorous trial design. A friend who knows no statistics asks you to explain this. 3. What is the difference between observational studies and experiments?
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A. In an observational study we assign some subjects to take supplements and assign the others to take no supplements. In an experiment we simply observe subjects who have chosen to take supplements and compare them with others who do not take supplements. B.
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This note was uploaded on 01/13/2012 for the course STATS 1107 taught by Professor James during the Fall '11 term at University of Georgia Athens.

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Chapter 8 hw stats - Ch 08 HW Your response has been submitted successfully Points Awarded 8 Points Missed 13 Percentage 38 1 How can we reduce the

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