Posted by **G.** on Thursday, June 19, 2008 at 5:14am.

In Dallas some fire trucks were painted yellow (not red) to heighten their visability. During a test period, the fleet of red fire trucks made 153,348 runs and had 20 accidents, while the fleet of yellow trucks made 135,035 runs and had 4 accidents. At a= .01, did the yellow fire trucks have a significantly lower accident rate? (a) state the hypothesis (b) state the decision rule and sketch it (c) find the 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 normally assumption fulfilled? Explain

Accident rate for Dallas Fire Trucks

Statistic Red Trucks Yellow Trucks

# of Accidentsx1=20accidents x2=4accid

# of fire runsn1=153,348 n2=135,035

- statistics -
**MathGuru**, Saturday, June 21, 2008 at 8:44pm
Hypotheses:

Ho: pY = pR (R = red trucks; Y = yellow trucks)

Ha: pY < pR

You can use a binomial proportion 2-sample z-test for this kind of problem.

Here is one formula for this type of test:

z = (pY - pR)/√(pq(1/n1 + 1/n2)

p = (x1 + x2)/(n1 + n2)

q = 1 - p

pY = 4/135035

pR = 20/153348

p = (4 + 20)/(135035 + 153348)

q = 1 - p

Convert to decimals and substitute into the formula. Calculate z. Compare to the cutoff z at .01 for a one-tailed test (Ha shows a specific direction, so the test is one-tailed). Determine the p-value, which is the actual level of the test statistic. Determine whether to reject Ho (the null hypothesis) or fail to reject Ho. If you reject Ho, then you accept Ha and the test is statistically significant.

I hope this will help get you started.

## Answer This Question

## Related Questions

- university phoenix - In Dallas, some fire trucks were painted yellow (instead ...
- Math - There were 12 new trucks brought to the sales lot on Monday. Three of ...
- Math - An explosion has occurred in Canada. Its blast radius was a regular ...
- Math - Mario replaced 72 tires on the small and large trucks in his fleet. He ...
- Geometry - A spherical storage tank has a diameter of 48 ft and is full of ...
- math - The CEO of a transportation company wants to use a large amount of cash ...
- Maths - The parts of a pole were painted red, blue and yellow. 3/5 was painted ...
- hard math - The jelly Junior school color is made by mixing red paint and yellow...
- Physics - 8. Fire engines used to be red. Yellow-green is now the preferred ...
- math - A florist had an equal number of red and yellow tulips. She sold 624 red ...

More Related Questions