# Question: A car magazine is comparing the total repair costs incurred

A car magazine is comparing the total repair costs incurred during the first three years on two sports cars, the T-999 and the XPY. Random samples of 45 T-999s and 51 XPYs are taken. All 96 cars are 3 years old and have similar mileages. The mean of repair costs for the 45 T-999 cars is $3300 for the first 3 years. For the 51 XPY cars, this mean is $3850. Assume that the standard deviations for the two populations are $800 and $1000, respectively.

a. Construct a 99% confidence interval for the difference between the two population means.

b. Using a 1% significance level, can you conclude that such mean repair costs are different for these two types of cars?

c. What would your decision be in part b if the probability of making a Type I error were zero? Explain.

a. Construct a 99% confidence interval for the difference between the two population means.

b. Using a 1% significance level, can you conclude that such mean repair costs are different for these two types of cars?

c. What would your decision be in part b if the probability of making a Type I error were zero? Explain.

## Answer to relevant Questions

The management at New Century Bank claims that the mean waiting time for all customers at its branches is less than that at the Public Bank, which is its main competitor. A business consulting firm took a sample of 200 ...Refer to the information given in Exercise 10.17. Test at a 5% significance level if the two population means are different. n1 = 21 1 = 13.97 s1 = 3.78 n2 = 20 2 = 15.55 s1 = 3.26 The standard recommendation for automobile oil changes is once every 3000 miles. A local mechanic is interested in determining whether people who drive more expensive cars are more likely to follow the recommendation. ...According to the credit rating agency Equifax, credit limits on newly issued credit cards increased between January 2011 and May 2011 (money.cnn.com/2011/08/19/pf/credit_card_issuance/index.htm). Suppose that random samples ...As mentioned in Exercise 10.26, a town that recently started a single-stream recycling program provided 60-gallon recycling bins to 25 randomly selected households and 75-gallon recycling bins to 22 randomly selected ...Post your question