The authors of the paper"Fudging the Numbers: Distributing Chocolate Influences Student Evaluations of an Undergraduate Course"carried out a study to see if events unrelated to an undergraduate course could affect student evaluations. Students enrolled in statistics courses taught by the same instructor participated in the study. All students attended the same lectures and one of six discussion sections that met once a week. At the end of the course, the researchers chose three of the discussion sections to be the "chocolate group." Students in these three sections were offered chocolate prior to having them fill out course evaluations. Students in the other three sections were not offered chocolate.

The researchers concluded that "Overall, students offered chocolate gave more positive evaluations than students not offered chocolate." Indicate whether the study is an observational study or an experiment. Give a brief explanation for your choice.

a. This is an observational study since all of the students received the chocolate.

b. This is an experiment since the investigators determining which discussion sections received the chocolate and which did not.

c. This is an observational study since the students didn't have to take the candy.

d. This is an experiment since the students were offered the chocolate before the evaluations.

The article"Why We Fall for This"described a study in which a business professor divided his class into two groups. He showed students a mug and then asked students in one of the groups how much they would pay for the mug. Students in the other group were asked how much they would sell the mug for if it belonged to them. Surprisingly, the average value assigned to the mug was quite different for the two groups! Indicate whether the study is an observational study or an experiment. Give a brief explanation for your choice.

a. This is an observational study since the professor observed the different values for buying and selling the mug.

b. This is an experiment since the professor determined who was supplying the buying price and who was supplying the selling price.

c. This is an observational study since the professor asked the entire class for values.

d. This is an experiment since the professor took the average of the values.