Dan Allen Drive is a major north-south artery through the NC State campus that connects Hillsborough Street and Western Boulevard. Campus police are concerned that vehicles traveling on Dan Allen Drive often exceed the posted speed limit of 20 miles per hour. To gather data on the speed of vehicles, campus police one day placed a radar speed detector by the side of Dan Allen and recorded the speed of cars over a 15-minute period.
The speeds are shown below:
24 29 29 23 25 24 33 26 24 29 27 26
22 32 24 21 19 29 31 26 29 31 16
Use the data above to construct a 95% confidence interval for the mean speed μ of vehicles traveling on Dan Allen Drive. (calculate y and s to 3 decimal places).