Question 4

The main advantage of experiments over observational studies is that:

A a well-designed experiment can give good evidence that the treatment actually causes the response.

B an experiment can compare two or more groups.

C an experiment is always cheaper.

D an experiment is always shorter.

E we can include more than one explanatory variable in the study.

Question 5

Students in a large statistics class were randomly divided into two groups. The first group had a midterm exam that was printed on canary paper while the second group had the exam printed on pale green paper. The exam scores of the two groups were then compared.

This experiment was not blind because:

A students were allowed to keep their eyes open while taking the exam.

B students were randomized into the two groups.

C some of the students did not study for the exam.

D the exam was too long.

E the students knew the color of paper on which their exam was printed.