Putting It Together: Online HomeworkProfessor Stephen Zuro of Joliet Junior College wanted to determine whether an online homework system improved scores on a final exam. In the fall semester, he taught a precalculus class using the online homework system (which meant students did their homework online and received instant feedback about their answers along with helpful guidance). In the spring semester, he taught a precalculus class without the homework system (which meant students were responsible for doing their homework the old-fashioned way—paper and pencil). Professor Zuro made sure to teach the two courses identically (same text, syllabus, tests, meeting time, meeting location, and so on). The table summarizes the results of the two classes on their final exam.

(a)What type of experimental design is this?

(b)What is the response variable? What are the treatments in the study?

(c)What factors are controlled in the experiment?

(d)In many experiments, the researcher will recruit volunteers and randomly assign the individuals to a treatment group. In what regard was this done for this experiment?

(e)Did the students perform better on the final exam in the fall semester? Use an a = 0.05 level of significance.

(f)Can you think of any factors that may confound the results?

Could Professor Zuro have done anything about these confounding factors?

Q1002

Testing Hypotheses Regarding Two Population Standard Deviations

An investor believes that Cisco Systems is a more volatile stock than General Electric. The volatility of a stock is measured by the standard deviation rate of return on the stock. The data in Table 6 represent the monthly rate of return between 1990 and 2010 for 10 randomly selected months for Cisco Systems stock and 14 randomly selected months for General Electric stock. Does the evidence suggest that Cisco Systems stock is more volatile than General Electric stock at the a = 0.05 level of significance?

Q1003

Testing Hypotheses Regarding Two Population Standard Deviations

In the Spacelab Life Sciences 2 payload, 14 male rats were sent to space.

Upon their return, the red blood cell mass (in milliliters) of the rats was determined. A control group of 14 male rats was held under the same conditions (except for spaceflight) as the space rats, and their red blood cell mass was likewise determined when the space rats returned. The project was led by Dr. Paul X. Callahan. The data in Table 7 were obtained.

Is the standard deviation of the red blood cell mass in the flight animals different from the standard deviation of the red blood cell mass in the control animals at the a = 0.05 level of significance?