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CHAPTER 1 SOLUTIONS AND MINI-PROJECT NOTES CHAPTER 1 THE BENEFITS AND RISKS OF USING STATISTICS EXERCISE SOLUTIONS 1.1 Because the men were randomly assigned to the two conditions (i.e., because it was a randomized experiment), the only substantial difference between the two groups should have been whether they took aspirin or a placebo. Therefore, the observed reduction in heart attack rates for those taking aspirin can be attributed to the difference in treatments. 1.2 a. No. People cannot be randomly assigned to attend cultural events or not. b. We cannot conclude that the relationship is causal because this is an observational study. There could be other factors that account for the increased longevity, for instance, maybe those who are already healthier are more likely to attend cultural events. c. The article implies that there is a causal connection and seeks an explanation. The causal link is not justified. d. Examples are general health at the start of the study and amount of exercise in their daily lives. (Maybe those who are healthier and who have more energy are more likely to exercise and to attend cultural events.) 1.3 If the measurements of interest are extremely variable in nature, then a large sample will be required in order to detect real differences between groups or treatments. 1.4 First, even if they all mailed the surveys back the results would apply only to subscribers to that magazine, and not to some larger population. Second, it is very unlikely that a large proportion will mail them back and those who do are most likely to be those with strong opinions. Therefore, the results cannot even be extended to all subscribers of that magazine. 1.5 a. It was most likely a randomized experiment. Placebos are not likely to be taken in observational studies. b.
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This note was uploaded on 10/15/2011 for the course STAT 100 at Pennsylvania State University, University Park.

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