Question

Many unversities and colleges have instituted supplemental instruction (SI) programs, in which 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 are randomly divided into a control group 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.

A) 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?
B) What do you think is the advantage of randomly dividing the students into the two groups rather than letting each student choose which group to join?
C) Why didn’t the investigators put all students in the treatment group?

Answer 1

Explanation:

SUPPLEMENTAL INSTRUCTION PROGRAMS

- Students in a large statistics course are randomly divided into a control group and an experimental/treatment group. At the end of the term, each student's score in the course is examined

(A) The scores from the SI (Experimental) group are not a sample from an existing population. They are data from a group in a sample, hence the sample here is the number of students tested in this experiment and that equates to all the students in the large Statistics course/class.

- The relevant conceptual population would be all students in the university, since the general purpose or statement of this experiment is to see the effect of SI programs implemented in universities.

(B) The advantage of the random (unintentional) division of the students into control and experimental groups is that results or scores from the groups will be unbiased.

If you let each student choose a group, there is a high probability that the serious students will all join the SI group while the unserious ones will choose to be in the control group.

There is also a high probability that brilliant/pompous students will ignore the supplemental instruction program while students with low and medium intelligence quotient (IQ) will embrace it.

It is also possible that students will join whatever group their friends join.

These and other biases will defeat the aim of the experiment.

(C) The investigators didn't put all students in the sample into the experimental group because the difference or impact of the SI program needs to be known; whether positive or negative. Dividing them into the 2 groups lets the investigators know if there is a difference in the scores of students in the two groups.