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1234567891011121314ABCt-Test: Two-Sample Assuming Equal VariancesSpeeds BeforeSpeeds AfterMean31.7431.42Variance4.504.41Observations100100Pooled Variance4.45Hypothesized Mean Difference0df198t Stat1.07P(T<=t) one-tail0.1424t Critical one-tail1.6526P(T<=t) two-tail0.2849t Critical two-tail1.9720t = 1.07, p-value = .1424. There is not enough evidence to infer that speed bumps reduce speeds. Proper stops: Equal-variances t-test of 21μ−μ0)(:H210=μ−μ0)(:H211<μ−μ⎟⎟⎠⎞⎜⎜⎝⎛+μ−μ−−=212p2121n1n1s)()xx(t1234567891011121314ABCt-Test: Two-Sample Assuming Equal VariancesStops BeforeStops AfterMean7.827.98Variance1.831.84Observations100100Pooled Variance1.83Hypothesized Mean Difference0df198t Stat-0.84P(T<=t) one-tail0.2021t Critical one-tail1.6526P(T<=t) two-tail0.4042t Critical two-tail1.9720t = –.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 μnstx2/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. 1234567ABCDt-Estimate: MeanPSIMean 4.20Standard Deviation1.93LCL3.93UCL4.46LCL = 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 Dμ0:HD0=μ0:HD1>μDDDDn/sxtμ−=1234567891011121314ABCt-Test: Paired Two Sample for MeansBeforeAfterMean28.9426.22Variance61.45104.30Observations5050Pearson Correlation0.87Hypothesized Mean Difference0df49t Stat3.73P(T<=t) one-tail0.000t Critical one-tail1.677P(T<=t) two-tail0.000t Critical two-tail2.010t = 3.73, p-value = .0002. There is enough evidence to infer that the law discourages bicycle use. A13.9 z -test of 21pp−(case 1)0)pp(:H210=−