(a)

Many universities and colleges have instituted supplemental instruction (SI) programs, in which a student facilitator meets regularly with a small group of students enrolled in the course to promote discussion of course material and enhance subject mastery. Suppose that students in a large statistics course (what else?) are randomly divided into a control group that will not participate in SI and a treatment group that will participate. At the end of the term, each student's total score in the course is determined.

Scenario: Many universities and colleges have instituted supplemental instruction (SI) programs, in which a student facilitator meets regularly with a small group of students enrolled in the course to promote discussion of course material and enhance subject mastery. Suppose that students in a large statistics course (what else?) are randomly divided into a control group that will not participate in SI and a treatment group that will participate. At the end of the term, each student's total score in the course is determined.

Problem: Are the scores from the SI group a sample from an existing population? If so, what is it? If not, what is the relevant conceptual population?

Answer: No. They are from the conceptual population of all students taking a large statistics course who participate in an SI program of this sort.

(b)

Problem: What do you think is the primary advantage of randomly dividing the students into the two groups rather than letting each student choose which group to join?

Answer: The two groups should be fairly comparable before the study.

(c)

Problem: Why didn't the investigators put all students in the treatment group?

Answer: To have some results to compare to each other.