Question: 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 had 135,035 runs and had 4 accidents. At a=.01, did the yellow fire trucks have significantly lower accident rate.

a) State the hypothesis.

b) State the rule and sketch it

c) Find the sample proportions and z test statistics

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