sol.hw7.stat3011 - Homework 7 Solutions Yicheng Kang...

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Unformatted text preview: Homework 7 Solutions Yicheng Kang November 2, 2010 8.6 a)The point estimate is the mean of the salaries of the sample of three students:$ 45,000. b)The interval would be:(20,200,69,800). It includes all salaries within one margin of error on either side of the mean. c)A point estimate alone may be highly inacurate, especially with a small sample. An interval estimate gives us a sense of the accuracy of the point estimate. 8.12 a) 17 / 987 = 0 . 017 b) p ˆ p (1- ˆ p ) /n = 0 . 0041 c)1 . 96 × . 0041 = 0 . 008. d)0 . 017 ± . 008. We can conclude that fewer than 10% of all adults in the U.S. were victims. 8.18 a) 1.645 b)2.33 c) 3.29 1 8.23 a) 660 / 1400 = 0 . 471 se = p ˆ p (1- ˆ p ) /n = 0 . 013 margin of error = 1 . 96 × . 013 = 0 . 025 confidence interval:(0.446,0.496). We could predict the winner because 0.50 falls outside of the confidence interval. It does not appear that the Democrats received more than half of the votes....
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sol.hw7.stat3011 - Homework 7 Solutions Yicheng Kang...

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