2. In an effort to reduce traffic jam, city planners have encouraged more people to take...

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2. In an effort to reduce traffic jam, city planners have encouraged more people to take public transit and to join car pools. Five years ago, before the planners began their campaign; the average speed of vehicles in the downtown area during rush hour was calculated to be 12 mph. To measure the effectiveness of the campaign, the speed of 40 motor vehicles were measured during rush hour in the down town area. Their average speed was 15 mph and the sample standard deviation was 7 mph. Can we conclude that rush hour traffic has moved faster after the city planners' advertising campaign? Use an a of 5%. 2. In an effort to reduce traffic jam, city planners have encouraged more people to take public transit and to join car pools. Five years ago, before the planners began their campaign; the average speed of vehicles in the downtown area during rush hour was calculated to be 12 mph. To measure the effectiveness of the campaign, the speed of 40 motor vehicles were measured during rush hour in the down town area. Their average speed was 15 mph and the sample standard deviation was 7 mph. Can we conclude that rush hour traffic has moved faster after the city planners' advertising campaign? Use an a of 5%.