invest_3ed.pdf

# A strong relationship between the size of the dose of

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a strong relationship between the size of the “dose” of smoking and occurrence of lung cancer for these patients. However, this study was criticized for “retrospective bias” in asking subjects to accura tely remember, and be willing to tell, details of their lifestyles. This can also be complicated by asking these questions of patients who know they have been diagnosed with lung cancer, as their recall may be affected by this knowledge. We also have to worry whether hospitalized males are representative of the male population. Other studies around the same time (e.g., Hammond and Horn, Wynder and Cornfield) found similar increases in “risk” with smoking. However, these were all observational studies so critics reasonably argued that other variables such as lifestyle, diet, exercise, and genetics could be responsible for both the smoking habits and the development of lung cancer. Although there was still much (on-going) research to be done, and these studies did not claim to prove that cigarette smoking causes lung cancer, these landmark studies set the stage. They also led to many efforts in improving study design and in developing statistical tools (such as relative risk and odds ratios) to analyze the results. Practice Problem 3.10A A researcher searched court records to find 908 individuals who had been victims of abuse as children (11 years or younger). She then found 667 individuals, with similar demographic characteristics, who had not been abused as children. Based on a search through subsequent years of court records, she determined how many in each of these groups became involved in violent crimes (Widom, 1989). The results are shown below: Abuse victim Control Involved in violent crime 102 53 Not involved in violent crime 806 614 (a) Is this an observational study or an experiment? If observational, which type? (b) Calculate and interpret the odds ratio of being involved in a violent crime between these two groups. (c) The one-sided p- value for this result (using Fisher’s Exact Test) is 0.018 (confirm). Is it reasonable to conclude that being a victim of abuse as a child causes individuals to be more likely to be violent toward others afterwards? Explain. (d) Calculate and interpret a 95% confidence interval for the population odds ratio. (e) Is it reasonable to generalize these results to all abuse and non-abuse victims? Explain.

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Chance/Rossman, 2015 ISCAM III Investigation 3.10 238 Practice Problem 3.10B (a) Suppose that individuals in Group 1 have a 2/3 probability of success, and those in Group 2 have a 1/2 probability of success. Calculate and interpret the relative risk of success, comparing Group 1 to Group 2. (b) Calculate and interpret the odds of success for Group 1. (c) Calculate and interpret the odds ratio of success, comparing Group 1 to Group 2.
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