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put this solution on YOUR website!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.
Ho: p(red)-p(yel) = 0
Ha: p(red)-p(yel) > 0
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(b) State the decision rule and sketch it.
Critical Value z = 2.3263 ; If T.S. > 2.3263,reject Ho.
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(c) Find the sample proportions and z test statistic.
P-hat(red) 20/153,035; p-hat(yel)=4/135,035
T.S. : z(diff) = 2.9610
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(d) Make a decision.
Reject Ho since T.S. > C.R.
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(e) Find the p-value and interpret it.
p-value = P(z>2.9610) = 0.0015..
Only 0.1% of test results could have given stronger support for rejecting Ho.
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(f) If statistically significant, do you think the difference is large enough to be important? If so, to whom, and why?
My opinion: Yes
Your opinion: ?
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(g) Is the normality assumption fulfilled? Explain.
Check your text.
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Cheers,
Stan H.
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