Fundamentals of Biostatistics
8th Edition
ISBN: 9781305268920
Author: Bernard Rosner
Publisher: Cengage Learning
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Chapter 8, Problem 67P
A clinical trial compared percutaneous transluminal coronary angioplasty (PTCA) with medical therapy in treating single-vessel coronary-artery disease [13]. Researchers randomly assigned 107 patients to medical therapy and 105 to PTCA. Patients were given exercise tests at baseline and after 6 months of follow-up. Exercise tests were performed up to maximal effort until clinical signs (such as angina) were present. The results shown in Table 8.21 were obtained for change in total duration of exercise (min) (6 months – baseline).
Table 8.21 Change in total duration of exercise for patients with coronary-artery disease randomized to medical therapy vs. PTCA
Perform the test in Problem 8.66 for the medical therapy group, and report a p-value.
8.66 What test can be performed to test for change in
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8
9.
-1
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-1.2
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A data set from a study that examined the effect of a specific diet on blood pressure is provided . Participants (n = 72) were randomly assigned either to a group that was put on the diet (Diet = Present) or to a group that was not put on the diet (Diet = Absent), and researchers wanted to know whether the diet had a significant impact on blood pressure.
Fully interpret the results in the context of this study (i.e., report the conclusions as related to the research question).
Reduced heart rate variability (HRV) is known to be a predictor of mortality after a heart attack. One measure of HRV is the average normal-to-normal beat interval (in milliseconds) for a 24-hr time period. Twenty-two heart attack patients who were dog owners and 80 heart attack patients who did not own a dog participated in a study of the effect of pet ownership on HRV, resulting in the summary statistics shown in the accompanying table.
The authors of this paper used a two-sample t test to test H0: ?1 − ?2 = 0 versus Ha: ?1 − ?2 ≠ 0.
What conditions must be met in order for this to be an appropriate method of analysis? (Select all that apply.)
Find the test statistic and P-value.
Chapter 8 Solutions
Fundamentals of Biostatistics
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- Reduced heart rate variability (HRV) is known to be a predictor of mortality after a heart attack. One measure of HRV is the average normal-to-normal beat interval (in milliseconds) for a 24-hr time period. Twenty-two heart attack patients who were dog owners and 80 heart attack patients who did not own a dog participated in a study of the effect of pet ownership on HRV, resulting in the summary statistics shown in the accompanying table.arrow_forwardReduced heart rate variability (HRV) is known to be a predictor of mortality after a heart attack. One measure of HRV is the average normal-to-normal beat interval (in milliseconds) for a 24-hr time period. Twenty-two heart attack patients who were dog owners and 80 heart attack patients who did not own a dog participated in a study of the effect of pet ownership on HRV, resulting in the summary statistics shown in the accompanying table. Measure of HRV(Average Normal-to-Normal Beat Interval) Mean StandardDeviation Owns Dog 871 134 Does Not Own Dog 800 138 (b) The paper indicates that the null hypothesis in part (a) was rejected and reported that the P-value was less than 0.05. Carry out a two-sample t test. (Use ? = 0.05. Use ?1 for heart attack patients who are dog owners and ?2 for heart attack patients who do not own a dog.) Find the test statistic and P-value. (Use SALT. Round your test statistic to one decimal place and your P-value to three decimal places.) t=…arrow_forwardTraumatic Brain Injury (TBI) is a significant health problem. TBI is caused by impacts to the head that might occurduring contact sports, motor vehicle accidents, and similar events. TBI is known to produce cognitive impairments and reductions in brain volume. In a recent, repeated-measures study on TBI, Zagorchev et al.(2016) observed that the size of the amygdala among mild TBI patients was reduced at 12 months after injury, relative to two months after injury. Suppose that a researcher is interested in replicating and extending this observation. She recruits n=8 participants with mild TBI and records the volume of a brain region at 2 months and again and again at 12 months. Her data are listed below a.) Test the hypothesis that volume of the brain region changed between 2 & 12 months. Use α=0.05, two-tailed b.) Compute the 80% confidence interval for the mean change in attention span for the populationarrow_forward
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