Which of the following is LEAST suited to providing clear evidence about a CAUSAL relationship between two variables?

The speed limit on interstate highways in the United States was reduced from 65 to 55 miles per hour in 1976. It was raised back to 65 in 1988; in 1996, individual state governments could decide the limit and many raised it to 75 miles per hour. Proponents and critics of the law have looked at the number of traffic deaths per 1000 miles driven on the highways between 1970 and 1998 to see whether the law affected traffic deaths. What type of design is this?

The classical experimental design contains all of the following, EXCEPT

Pete wanted to see whether caffeine intake increased a subject’s arousal state. He randomly assigned 100 high school seniors to an experimental or control group. The experimental group drank a high caffeine soda, while the control group drank a caffeine-free soda. He then measured and compared arousal states for both groups. What type of design did Pete use?

What are “demand characteristics” in experimental research?

Dr. Duffy conducted an experiment to raise I.Q. scores by having experimental subjects eat three bananas a day for a month, while control groups had no bananas. Below are his results (scores = average I.Q. score for group of subject). Which of the following can you say about the results?

Dr. Useem designed an experiment on group competition to be realistic. She divided subjects into 6 three- person teams. Only one could “win” a race to assemble a large complex toy. She wanted subjects to get “caught up” in the situation so it would have a large impact on them. A confederate posed as the vice president of a toy manufacturer who offered each member of the winning team $300, but members of the 5 losing teams got nothing. She’s trying to create

Dr. Bootsma designed and produced a 30 second radio commercial for a local automobile dealer. Next, she had the three most widely listened to radio stations in town play the commercial 15 times a day, everyday, for two weeks. She waited until the end of the two-week period, then she called Jack to see what his sales had been lately. What experimental design did she use?

The following design notation for an experimental design is called 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0

Dr. Marshall conducted an experiment to test changes in sex roles due to spending an entire day reading about the achievements of great women artists and scientists. The experimental group read fifteen articles about great women. The control group read fifteen articles about cooking, automobiles, astronomy, and accounting. During the lunch break, subjects from the experimental and control groups met and talked about what they were reading. What internal validity problem may occur?