35. An epidemiologist was interested in determining whether aspirin was associated with an increased risk of gastrointestinal (GI) bleeding. She relied on primary physicians to identify 600 patients at a hospital who were taking a daily dose of aspirin and 600 other patients who were not taking aspirin. Subjects were followed for 1 year to detect any occurrences of GI bleeding in this cohort study. Due to publicity about the risk of bleeding associated with aspirin, primary physicians treating patients at the hospital followed their patients who were taking aspirin more closely than they were unexposed subjects. Which of the following describes the impact that this may have on the epidemiologist’s study? (3 points) A. Would introduce recall bias B. Would result in differential classification of exposure C. Would result in differential classification of outcome D. Would result in nondifferential classification of exposure E. Would result in nondifferential classification of outcome
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An epidemiologist is conducting a cohort study to determine if there is an association between aspirin use and an increased risk of gastrointestinal (GI) bleeding. The study involves two groups of patients: 600 who are taking aspirin and 600 who are not. The Show more…
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A well-known study of 22,000 male physicians was conducted to determine if taking aspirin daily reduces the chances of a heart attack. Half of the physicians were given a regular dose of aspirin while the other half was given placebos. Six years later, among those who took aspirin, 104 suffered heart attacks while among those who took placebos, 189 suffered heart attacks. (a) At α=0.01 level of significance test hypothesis if the aspirin can reduce the number of heart attacks among the sample group that took aspirin? Write the hypotheses for the test. Calculate the test statistic. Identify the critical value(s) for this test. Compare the critical value to the test statistic. Should the null hypothesis be rejected? Estimate the P value for the test and support your conclusion in the previous part using P value approach. (b)Find 99% confidence interval for the difference in proportions of physicians who suffered heart attacks after six years of taking aspirin and placebos.
Sri K.
The two-way table below provides findings of a randomized clinical trial testing the effect of aspirin intake on the risk of heart attack. Please note that the randomization procedure was very effective. Heart Attack No Heart Attack Total Aspirin 130 10,110 10,240 Placebo 170 10,102 10,272 total 300 20,212 20,512 Based on data presented in the table and assuming the randomization was effective, which of the following is true? A. The risk of heart attacks for the placebo group is increased by 77% B. The risk of heart attacks for the treatment group is decreased by about 77% as compared to those in the placebo group. C. Although there seems to be a difference in the risk of heart attack between the treatment and placebo groups, the difference might be due to variations in baseline characteristics. D. The risk of heart attacks for the treatment group is decreased by about 23% as compared to those in the placebo group
Sheryl E.
Physician's Health Study In the Physician's Health Study, introduced in Data 1.6 on page 37 , 22,071 male physicians participated in a study to determine whether taking a daily low-dose aspirin reduced the risk of heart attacks. The men were randomly assigned to two groups and the study was double-blind. After five years, 104 of the 11,037 men taking a daily low-dose aspirin had had a heart attack while 189 of the 11,034 men taking a placebo had had a heart attack. ${ }^{39}$ Does taking a daily lowdose aspirin reduce the risk of heart attacks? Conduct the test, and, in addition, explain why we can infer a causal relationship from the results.
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