Volkswagen has created a series of videos based on its “fun theory,” the idea that you can change behavior if you take an activity that is good for society and makeit fun. (You can watch the videos at http://www.thefuntheory.  com/.) For each of the following examples, state the independent variable (and its levels) as well as the dependent variable (and the types of variables that both of these are). Then, state whether you could use an independent-samples t test to analyze the data, and explain your answer.

a. A “Speed Camera Lottery”—in which an electronic sign told people how fast they were going so they could adjust their speed—was introduced. As people passed the electronic sign, a camera took a photo of their license plate. If they were speeding, they were mailed a ticket and had to pay a fine. If they were obeying the speed limit, they were entered into a lottery to win some of the money from those who paid speeding tickets. The average speed using the Speed Camera Lottery sign was 25 kilometers per hour, and the average speed with no lottery sign was 32 kilometers per hour.

b. At the exit of a subway station, stairs and an escalator were side by side. The stairs were turned into a piano, so that when you climbed them, you heard musical notes. While the Piano Staircase was in place, 66% more people took the stairs—rather than the escalator— than when the Piano Staircase was not in place.

c. A trash bin was designed so that when someone threw trash into it, there was a long whistling sound, followed by a thud, as if the trash were falling into an extremely deep bin. When the bin was used, an average of 72 kg of trash was disposed of in a day; when it was not used, an average of 31 kg of trash was disposed of in a day.