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Z test for proportion : Fire trucks

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 25 accidents, while the fleet of yellow fire trucks made 135,035 runs and had 5 accidents. At α = .01, did the yellow fire trucks have a significantly lower accident rate?

Accident Rate for Dallas Fire Trucks:

Statistic Red Fire Trucks Yellow Fire Trucks
Number of accidents x1 = 25 accidents x2 = 5 accidents
Number of fire runs n1 = 153,348 runs n2 = 135,035 runs

RQ: Do the yellow fire trucks have significantly lower accident rates than red fire trucks?

A. Choose the Hypothesis

B. Specify the Decision Rule

C. Calculate the Test Statistic

D. Make the Decision

E. Give an interpretation of the Decision

F. P-value Method
1. Calculate the P-value, what is it?

2. Does that P-value support the Decision in Part D?

Solution Summary

The solution provides step by step method for the calculation of Z test for proportion . Formula for the calculation and Interpretations of the results are also included. Interactive excel sheet is included. The user can edit the inputs and obtain the complete results for a new set of data. This question is from the e-text Applied Statistics in Business and Economics, by Doane and Seward