Refer to Exercise 6.64. The small number of vehicles in the study has led to criticism o...

Refer to Exercise 6.64. The small number of vehicles in the study has led to criticism of the results. A new study is to be conducted with a larger sample size. Assume that the populations of damages are both normally distributed with a common σ = $700.

a. Determine the sample size so that we are 95% confident that the estimate of the difference in mean repair cost is within $500 of the true difference.

b. For the research hypothesis determine the sample size required to obtain a test having α = .05 and

REFERENCE:

6.64 : Many people purchase sports utility vehicles (SUVs) because they think they are sturdier and hence safer than regular cars. However, preliminary data have indicated that the costs for repairs of SUVs are higher than for midsize cars when both vehicles are in an accident. A random sample of 8 new SUVs and 8 midsize cars are tested for front impact resistance. The amounts of damage (in hundreds of dollars) to the vehicles when crashed at 20 mph head on into a stationary barrier are recorded in the following table.

a. Plot the data to determine whether the conditions required for the t procedures are valid.

b. Do the data support the conjecture that the mean damage is greater for SUVs than for midsize vehicles? Use α = .05 with both the t test and Wilcoxon test.

c. Which test appears to be the more appropriate procedure for this data set?

d. Do you reach the same conclusions from both procedures? Why or why not?