In Exercises 1.17–1.22, state whether the investigation in question is an observational study or a designed experiment. Justify your answer in each case.
Heart Failure. In the paper “Cardiac-Resynchronization Therapy with or without an Implantable Defibrillator in Advanced Chronic Heart Failure” (New England Journal of Medicine, Vol. 350, pp. 2140–2150), M. Bristow et al. reported the results of a study of methods for treating patients who had advanced heart failure due to ischemic or nonischemic cardiomyopathies. A total of 1520 patients were randomly assigned in a 1:2:2 ratio to receive optimal pharmacologic therapy alone or in combination with either a pacemaker or a pacemaker–defibrillator combination. The patients were then observed until they died or were hospitalized for any cause.
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Introductory Statistics (10th Edition)
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- King Tut was an ancient Egyptian ruler whose tomb was discovered and opened in 1923. Legend has it that the archaeologists who opened the tomb were subject to a “mummy's curse,” which would shorten their life spans. The article “The Mummy’s Curse: Historical Cohort Study” (M. Nelson, British Medical Journal, 2002:1482–1484) presents an investigation of the mummy’s curse. The article reports that 25 people exposed to the curse had a mean life span of 70.0 years with a standard deviation of 12.4 years, while a sample of 11 Westerners in Egypt at the time who were not exposed to the curse had a mean life span of 75.0 years with a standard deviation of 13.6 years. Can you conclude that the mean life span of those exposed to the mummy’s curse is less than the mean of those not exposed?arrow_forwardA diabetic nurse seeks to assess the prevalence of type 2 diabetes among women in a population (age 18 to 80 years). She conveniently sampled 100 women attending antenatal care and asked them whether they had hypertension. Of the 100 pregnant women sampled, 50 consented to take part in the study and 1 had diabetes. Based on this finding, the nurse concluded that “the prevalence of diabetes among women in the population is low (2%).” A) Do you agree with the conclusion made by the diabetic nurse? Justify in not more than 100 words? B) Would you have conducted such a study differently if you had all the resources at hand (Describe in not more than 75 words).arrow_forwardTwo groups, A and B, consist of 100 people each who have a disease. A serum is given to group A but not to group B (which is called the control). It is found that in groups A and B, 75 and 65 people, respectively, recover from the disease. At significant levels of (a) 0.01, (b) 0.05, test the hypothesis that the serum helps cure the disease.arrow_forward
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