Safety researchers, interested in determining whether the occupancy of a vehicle might be related to the speed at which the vehicle is driven, have observed the following speed (mph) measurements for two random samples of vehicles. (Use data file XR12030.)

Driver alone 64 50 71 55 67 61 80 56 59 74

At least one passenger 44 52 54 48 69 67 54 57 58 51 62 67

a. What are the null and alternative hypotheses for this test?

b. Use ANOVA and the 0.025 level of significance in testing the null hypothesis identified in part (a). 

c. For each sample, construct the 95% confidence interval for the population mean.