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Week 3 Problems

# Week 3 Problems - Week 3 Problems 10.30 In Dallas some fire...

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Week 3 Problems 10.30 In Dallas, some fire trucks were painted yellow (instead of red) to heighten their visibility. During a test period, the fleet of red fire trucks made 153,348 runs and had 20 accidents, while the fleet of yellow fire trucks made 135,035 runs and had 4 accidents. At α = .01, did the yellow fire trucks have a significantly lower accident rate? (a) State the hypotheses. (b) State the decision rule and sketch it. (c) Find the sample proportions and z test statistic. (d) Make a decision. (e) Find the p -value and interpret it. (f) If statistically significant, do you think the difference is large enough to be important? If so, to whom, and why? (g) Is the normality assumption fulfilled? Explain. = = p c z if Ho ject b p p Ha p p Ho a ) 326 . 2 Re ) : : ) 2 1 2 1 b) Critical Value z = 2.3263 ; If T.S. > 2.3263,reject Ho. c) P-hat(red) 20/153,035; p-hat(yel)=4/135,035 T.S. : z(diff) = 2.9610 10.44 Does lovastatin (a cholesterol-lowering drug) reduce the risk of heart attack? In a Texas study, researchers gave lovastatin to 2,325 people and an inactive substitute to 2,081 people (average age 58). After 5 years, 57 of the lovastatin group had suffered a

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