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Bluman 5th_Chapter 7 HW Soln

Bluman 5th_Chapter 7 HW Soln - Math 227 Elementary...

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Math 227 Elementary Statistics: A Brief Version, 5/e Bluman Ch 7.1 pg. 364 #11, 13, 15, 17, 19, 21, 23, 25 11. Reading Scores : A sample of the reading scores of 35 fifth-graders has a mean of 82. The standard deviation of the sample is 15. Note: All values we calculated were rounded. a) Find the best point estimate of the mean. X Is the best point estimate for , therefore, the best point estimate of the population mean is 82 b) Find the 95% confidence interval of the mean reading scores of all the fifth-graders. n=35, Confidence interval (C.I.) = 0.95, 82, 15 x s /2 0.05 0.05 0.025 2 2 1 0.025 0.975 ( ) 1.96 Z /2 /2 [ ] [ ] s s X Z X Z n n 15 15 82 [1.96 ] 82 [1.96 ] 35 35 77 87 c) Find the 99% confidence interval of the mean reading scores of all fifth graders. /2 0.99 ( ) 0.495 2 Z To find go to table E and look for area = .4950, the corresponding z value for this area is 2.58. /2 /2 [ ] [ ] X Z X Z n n 82 [2.58 (2.5355)] 82 [2.58 (2.5355)] /2 Z /2 2.58 Z 0.95 /2 1.96 Z 0.025 0.975 0.95

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