Test the proportions of yellow fire trucks have a significantly lower accident rate.
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 = .01, did the yellow fire trucks have a significantly lower accident rate?
(a) Declare the hypotheses.
(b)State the decision rule and sketch it.
(c)Find out the sample proportions and z test statistic.
(d)Make a decision.
(e)Find out the pvalue 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? describe.
Accident Rate for Dallas Fire Trucks



Statistic

Red Fire Trucks

Yellow Fire Trucks

Number of accidents

x_{1} = 20 accidents

x_{2} = 4 accidents

Number of fire runs

n_{1 }= 153,348 runs

n_{2} = 135,035 runs
