1 2 3 4 5 6 7 8 9 10 11 12 13 14 a b c t test two

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 A B C t-Test: Two-Sample Assuming Equal Variances Speeds Before Speeds After Mean 31.74 31.42 Variance 4.50 4.41 Observations 100 100 Pooled Variance 4.45 Hypothesized Mean Difference 0 df 198 t Stat 1.07 P(T<=t) one-tail 0.1424 t Critical one-tail 1.6526 P(T<=t) two-tail 0.2849 t Critical two-tail 1.9720 t = 1.07, p-value = .1424. There is not enough evidence to infer that speed bumps reduce speeds. Proper stops: Equal-variances t-test of 2 1 μ μ 0 ) ( : H 2 1 0 = μ μ 0 ) ( : H 2 1 1 < μ μ + μ μ = 2 1 2 p 2 1 2 1 n 1 n 1 s ) ( ) x x ( t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 A B C t-Test: Two-Sample Assuming Equal Variances Stops Before Stops After Mean 7.82 7.98 Variance 1.83 1.84 Observations 100 100 Pooled Variance 1.83 Hypothesized Mean Difference 0 df 198 t Stat -0.84 P(T<=t) one-tail 0.2021 t Critical one-tail 1.6526 P(T<=t) two-tail 0.4042 t Critical two-tail 1.9720 t = –.84, p-value = .2021. There is not enough evidence to infer that speed bumps increase the number of proper stops. A13.7 t-estimator of μ n s t x 2 / α ±
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337 This edition is intended for use outside of the U.S. only, with content that may be different from the U.S. Edition. This may not be resold, copied, or distributed without the prior consent of the publisher. 1 2 3 4 5 6 7 A B C D t-Estimate: Mean PSI Mean 4.20 Standard Deviation 1.93 LCL 3.93 UCL 4.46 LCL = 3.93, UCL = 4.46. We estimate that on average tires are between 3.93 and 4.46 pounds per square inch below the recommended amount. Tire life: LCL = 100(3.93) = 393, UCL = 100(4.46) = 446. We estimate that the average tire life is decreased by between 393 and 446 miles. Gasoline consumption: LCL = .1(3.93) = .393, UCL = .1(4.46) = .446. We estimate that average gasoline consumption increases by between .393 and .446 gallons per mile. A13.8 t-test of D μ 0 : H D 0 = μ 0 : H D 1 > μ D D D D n / s x t μ = 1 2 3 4 5 6 7 8 9 10 11 12 13 14 A B C t-Test: Paired Two Sample for Means Before After Mean 28.94 26.22 Variance 61.45 104.30 Observations 50 50 Pearson Correlation 0.87 Hypothesized Mean Difference 0 df 49 t Stat 3.73 P(T<=t) one-tail 0.000 t Critical one-tail 1.677 P(T<=t) two-tail 0.000 t Critical two-tail 2.010 t = 3.73, p-value = .0002. There is enough evidence to infer that the law discourages bicycle use. A13.9 z -test of 2 1 p p (case 1) 0 ) p p ( : H 2 1 0 =
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