STAT 301 - Business Statistics
Lecture Review #18 - Principles of Experimental Design

Review questions:

1) Briefly explain/illustrate each of the following concepts:

• a) controlled experiment
• b) observational study
• c) control group
• d) replication
• e) randomization
• f) unit of analysis
• g) proxy variable

2) What are the relative advantages/disadvantages of a controlled experiment vs. an observational study? Of retrospective vs. prospective studies?

3) What is meant by the independent and dependent variables in a study? What are covariates?

Review exercises:

In each of the following, indicate (a) whether this is a controlled experiment, retrospective observational study, or prospective observational study; (b) identify the unit of analysis in the study; (c) list the variables in the study, indicating which are independent, dependent, and/or covariates; and (d) identify the population to which the sample result can be generalized.

1) Varsity intercollegiate athletes must devote a lot of time to their sport. Officials at the University of Southern North Dakota at Hoople are concerned about the extent to which this may affect the student-athlete's academic success. They investigate by pulling student records from the last academic year. For each student at the school, they obtain the grade point average (gpa) over all classes taken during the school year. They also identify whether each student is on an intercollegiate athletic team. They realize that some majors are tougher than others (the school’s flycasting major, for example, is not nearly as demanding as the basketweaving major), and so the obtain data on student major as well. Since some students have better academic aptitude or preparation, they also note each student’s high school grade point average and SAT score. They also record the student’s gender, and which (if any) sport s/he plays.

2) Horatio Wajberlinski read that playing classical music (specifically, Mozart) to infants makes them smarter. He theorizes that playing country "music" to them probably makes them dumber. He poses as a child psychology professor and convinces twenty gullible mothers to let him experiment on their babies — by telling them that "studies prove that playing music to your babies makes them smarter, and I know that you want to give your child every advantage that you can." Ten of the mothers are given a CD of country "music" and told to play that in the child’s hearing for at least one hour a day. The other ten are given a CD that contains nothing but silence. ("It’s specially recorded to tap directly into the child’s subconscious," he tells the mothers.) At the end of six months Horatio administers an IQ test specially designed for infants to each of the subjects. (Regardless of actual test results, he tells each of the moms that the test shows their child has "near genius-level IQ." Horatio was absent the week they covered research ethics in his research methods class.)