HW4 Solns - cell phone usage (and presence/absence of...

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Assignment 4 Solutions 8.17. (a) This is an observational study: Beahvior (alcohol consumption) is observed, but no treatment is imposed. 8.18. (c) This study shows an association between the two, but not a cause-and-effect relationship. 8.19. (b) The sample is the group about which we have information. 8.20. (a) The population is the group about which we wish to learn. 8.21. (c) The sample is the group from which we received responses, not the group from which we solicited responses. 8.22. (b) A voluntary response sample is typically biased, so we can draw few conclusions about the population. 8.23. (a) Each member of the population needs a three-digit label, and we need 440 of them—not 441 labels, as in (b). 8.24. (c) Take two digits at a time, and ignore unused and duplicate labels. 8.25. (a) Take four digits at a time, and ignore unused labels. 8.26. (b) Those without phones or with unlisted numbers—39% of the population—cannot be included in the sample. 9.16. (a) This is an observational study: No treatment was assigned to the subjects; we merely observed
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Unformatted text preview: cell phone usage (and presence/absence of cancer). 9.17. (b) This is an experiment (a treatment is imposed), but there is no control group for comparison. 9.18. (b) There are two factors, each with two levels, which yields the four treatments listed. 9.19. (a) We choose randomly from all subjects at once (rather than grouping them in blocks), and each subject gets one treatment (there is no pairing). 9.20. (c) The response variable is the effect we want to observe: How blood pressure changes in response to the various treatments. 9.21. (a) Each of the 36 subjects needs a label. 9.22. (b) The communities are paired up, then one is chose to have the advertising campaign. 9.23. (a) The choice should be made randomly. 9.24. (b) This was a (matched pairs) experiment, but in order to give useful information, the subjects should be chosen from those who might be expected to buy this car....
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