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Unformatted text preview: Assignment 5 Due date: 25 November 2009 Total number of points: 21 Q 1. (7.11) A study was conducted to determine whether relaxation training, aided by biofeedback and meditation, could help in reducing high blood pressure Subjects were randomly allocated to a biofeedback group or a control group. The biofeedback group received training for eight weeks. The table reports the reduction in systolic blood pressure (mm Hg) after eight weeks. (a) Compute estimated standard error of the difference in mean. (b) Construct a 95% confidence interval for the difference in mean response. (c) Interpret the confidence interval in (a). Biofeedback Control n 1 =69 n 2 =73 ¯ y 1 = 13 . 8 ¯ y 2 = 4 . SE ¯ y 1 = 1 . 34 SE ¯ y 2 = 1 . 30 Solution to Q1: (a) SE ¯ y 1 ¯ y 2 = p 1 . 34 2 + 1 . 3 2 = 1 . 867. (b) Number of degrees of freedom=140. Confidence interval: (6.1;13.5) (c) We are 95% confident that the population mean reduction in systolic blood pressure for those who receive training for eight weeks is larger than for others by an amount that might be as small as 6.1 mm Hg or as large as 13.5 mm Hg. Marking scheme for Q1: 1 point for the correct answer in part (a), 2 point for part (b), 1 point for part (c). Total: 4 points. Q 2. (7.30) In a study of the periodical cicada, researchers measured the hind tibia lengths of the shed skins of 110 individuals. Results for males and females are shown in the table: Male Female n 1 =60 n 2 =50 ¯ y 1 = 78 . 42 ¯ y 2 = 80 . 44 s 1 = 2 . 87 s 2 = 3 . 52 (a) Use ttest to investigate the dependence of tibia length on gender in this species. Usetest to investigate the dependence of tibia length on gender in this species....
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 Fall '09
 Kulik
 Statistics

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