(b): A taxi company is trying to decide whether the use of radial tires instead of regular belted tires improves fuel economy. Twelve cars were equipped with radial tires and driven over a prescribed test course. Without changing drivers, the same cars were then equipped with regular belted tires and driven once again over the test course. At 0.025 level, can we conclude that cars equipped with radial tires give better fuel economy than those equipped with belted tires. Assume the populations to be normally distributed. The gasoline consumption, in kilometers per liter, was recorded as follows: Kilometers per liter No. of cars Radial tires Belted tires 1 4.2 4.1 4.7 4.9 3 6.6 6.2 4 7.0 6.9 6.7 6.8 4.5 4.4 7 5.7 5.7 8 6.0 5.8 7.4 6.9 10 4.9 4.7 11 6.1 6.0 12 5.2 4.9

A purchasing manager for a large university is investigating which brand of LCD projector to purchase to equip their classrooms. Of major concern is the longevity of the light bulbs used in the projectors. The purchasing manager has narrowed down the choice of projector to two brands, Infocus and Proxima, and wishes to determine if there is any difference between the two brands in the mean lifetime of the bulbs used. The purchasing manager obtained thirteen projectors of each brand for testing over the last several academic terms. The number of hours the bulbs lasted on each of the thirteen projectors is given in the table. Lifetimes of light bulbs (hours) Infocus 830, 867, 1013, 986, 819, 809, 691, 903, 673, 909, 957, 820, 715 Proxima 532, 718, 769, 806, 779, 970, 903, 1043, 947, 792, 841, 752, 689 Send data to calc... v Send data to Excel Assume that the two populations of lifetimes, are normally distributed and that the population variances are equal. Can we conclude, at the 0.01…

In a population-based cohort study, an entire community was interviewed regarding smoking habits and then followed for one year. Upon ascertainment of all lung cancer deaths, the investigator obtained the following data:     Number of Individuals Lung Cancer Deaths Smokers 24,500 15 Nonsmokers 10,500 2   Calculate the risk difference per 100,000 per year. Round to the tenth decima

A purchasing manager for a large university is investigating which brand of LCD projector to purchase to equip their classrooms. Of major concern is the longevity of the light bulbs used in the projectors. The purchasing manager has narrowed down the choice of projector to two brands, Infocus and Proxima, and wishes to determine if there is any difference between the two brands in the mean lifetime of the bulbs used. The purchasing manager obtained eight projectors of each brand for testing over the last several academic terms. The number of hours the bulbs lasted on each of the eight projectors is given in the table. Lifetimes of light bulbs (hours) Infocus 745, 955, 1085, 756, 901, 839, 858, 931 Proxima 1012, 988, 957, 920, 878, 1130, 657, 743 Send data to calculator Assume that the two populations of lifetimes are normally distributed and that the population variances are equal. Can we conclude, at the 0.01 level of significance, that u, the mean lifetime of light bulbs in Infocus…