# Question

According to the information given in Exercise 10.25, a sample of 45 customers who drive luxury cars showed that their average distance driven between oil changes was 3187 miles with a sample standard deviation of 42.40 miles. Another sample of 40 customers who drive compact lower-price cars resulted in an average distance of 3214 miles with a standard deviation of 50.70 miles. Suppose that the standard deviations for the two populations are not equal.

a. Construct a 95% confidence interval for the difference in the mean distance between oil changes for all luxury cars and all compact lower-price cars.

b. Using a 1% significance level, can you conclude that the mean distance between oil changes is lower for all luxury cars than for all compact lower-price cars?

c. Suppose that the sample standard deviations were 28.9 and 61.4 miles, respectively. Redo parts a and b. Discuss any changes in the results.

a. Construct a 95% confidence interval for the difference in the mean distance between oil changes for all luxury cars and all compact lower-price cars.

b. Using a 1% significance level, can you conclude that the mean distance between oil changes is lower for all luxury cars than for all compact lower-price cars?

c. Suppose that the sample standard deviations were 28.9 and 61.4 miles, respectively. Redo parts a and b. Discuss any changes in the results.

## Answer to relevant Questions

The following information is obtained from two independent samples selected from two populations. n1 = 650 1 = 1.05 σ1 = 5.22 n2 = 675 2 = 1.54 σ1 = 6.80 a. What is the point estimate of µ1 – µ2? b. Construct a 95% ...Refer to Exercise 10.30. Now assume that the shredding times for both paper shredders are normally distributed with unequal and unknown standard deviations. a. Construct a 99% confidence interval for the difference between ...Perform the following tests of hypotheses, assuming that the populations of paired differences are normally distributed. a. H0: µd = 0, H1: µd ≠ 0, n = 9, = 6.7, sd = 2.5, α = .10 b. H0: µd = 0, H1: µd > 0, n = 22, ...What is the shape of the sampling distribution of p̂1 – p̂2 for two large samples? What are the mean and standard deviation of this sampling distribution? A sample of 1000 observations taken from the first population gave x1 = 290. Another sample of 1200 observations taken from the second population gave x2 = 396. a. Find the point estimate of p1 – p2. b. Make a 98% ...Post your question

0