A random sample of 21 AP® Statistics teachers was asked to report the age (in years) and mileage of their primary vehicles. Here is a scatterplot of the data:

Here is some computer output from a least-squares regression analysis of these data. Assume that the conditions for regression inference are met.

a. Verify that the 95% confidence interval for the slope of the population regression line is (9016.4, 14,244.8).

b. A national automotive group claims that the typical driver puts 15,000 miles per year on his or her main vehicle. We want to test whether AP® Statistics teachers are typical drivers. Explain why an appropriate pair of hypotheses for this test is H₀:β₁ = 15,000 versus H_a:β₁ ≠ 15,000.

c. Compute the standardized test statistic and P -value for the test in part (b). What conclusion would you draw at the α = 0.05 significance level?

d. Does the confidence interval in part (a) lead to the same conclusion as the test in part (c)? Explain your answer.

Transcribed Image Text:

150,000 120,000 90,000 60,000 30,000 2.5 5.0 7.5 10.0 Car age (yr) Mileage ....