A are there effects of second hand smoke on the

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(a) Are there effects of second-hand smoke on the health of children? (b) Do people tend to spend more money in stores located next to food outlets with pleasing smells? (c) Does cell phone use increase the rate of automobile accidents? (d) Do people consume different amounts of ice cream depending on the size of the bowl used? Practice Problem 3.5B Researchers conducted a randomized, double-blind trial to determine whether taking large amounts of Vitamin E protects against prostate cancer ( Journal of the National Cancer Institute, 1998). To study this question, they enrolled 29,133 Finnish men, all smokers, between the ages of 50 and 69. The men were divided into two groups: One group took vitamin E and a second group took a placebo. The researchers followed all the men for eight years and then determined how many had developed prostate cancer. They found that participants taking vitamin E were significantly less likely to develop prostate cancer. (a) Explain what “randomized” means in this study and its purpose. (b) Explain what “double - blind” means in the context of this study and its purpose. (c) Explain what “significantly less likely” means in the context of this study. (d) Based on this report, is it reasonable to conclude that taking vitamin E causes a reduction in the probability of developing prostate cancer? Explain your reasoning. (e) Based on this report, what population is it reasonable to generalize these results to? Explain your reasoning.
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Chance/Rossman, 2015 ISCAM III Investigation 3.6 210 SECTION 3: COMPARING TWO TREATMENT PROBABILITIES In the previous section, we saw potential benefits to using random assignment creating groups that we are willing to consider equivalent. However, there is still the chance that “luck of the draw” could lead to a higher success proportion for the response variable in one group. In this section you will explore a method for calculating p-values that addresses how often random assignment could create a difference between the treatment groups at least as large as the one observed. Investigation 3.6: Dolphin Therapy Antonioli and Reveley (2005) investigated whether swimming with dolphins was therapeutic for patients suffering from clinical depression. The researchers recruited 30 subjects aged 18-65 with a clinical diagnosis of mild to moderate depression through announcements on the internet, radio, newspapers, and hospitals in the U.S. and Honduras. Subjects were required to discontinue use of any antidepressant drugs or psychotherapy four weeks prior to the experiment, and throughout the experiment. These 30 subjects went to an island off the coast of Honduras, where they were randomly assigned to one of two treatment groups. Both groups engaged in one hour of swimming and snorkeling each day, but one group (Dolphin Therapy) did so in the presence of bottlenose dolphins and the other group (Control) did not. At the end of two weeks, each subject ’s level of depression was evaluated, as it had been at the
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