Name: Class: Date: 1. Use Scenario 4-6. Explain why this is an experiment and not an observational study.

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1 Name: Class: Date: Chapter 4 Review Short Answer Scenario 4-6 Read the following brief article about aspirin and alcohol. Aspirin may enhance impairment by alcohol Aspirin, a long time antidote for the side effects of drinking, may actually enhance alcohol s effect, researchers at the Bronx Veterans Affairs Medical Center say. In a report on a study published in the Journal of the American Medical Association, the researchers said they found that aspirin significantly lowered the body s ability to break down alcohol in the stomach. As a result, five volunteers who had a standard breakfast and two extra-strength aspirin tablets an hour before drinking had blood alcohol levels 30 percent higher than each had when they drank alcohol alone. Each volunteer consumed the equivalent of a glass and a half of wine. That 30 percent could make the difference between sobriety and impairment, said Dr. Charles S. Lieber, medical director of the Alcohol Research and Treatment Center at the Bronx center, who was co-author of the report with Dr. Risto Roine. 1. Use Scenario 4-6. Explain why this is an experiment and not an observational study. 2. Use Scenario 4-6. Identify the explanatory and response variables. 3. Use Scenario 4-6. Identify the experimental design used in this study. Justify your answer. 4. Use Scenario 4-6. In the second sentence above is the phrase, researchers said they found that aspirin significantly lowered the body s ability to break down alcohol What is the statistical meaning of the word significantly in the context of this study? 5. Use Scenario 4-6. This was a controlled experiment. Describe how it was controlled and explain the purpose of doing so. 1

2 Name: Scenario 4-7 High blood pressure adds to the workload of the heart and arteries and may increase the risk of heart attacks. If not treated, this condition can also lead to heart failure, kidney failure, or stroke. We wish to test the effectiveness of Angiotensin-converting enzyme (ACE) inhibitors as a treatment for high blood pressure. 6. Use Scenario 4-7. It is well known that men and women may react differently to common cardiovascular drug treatments. What sort of experimental design would you choose for this study, and why? 7. Use Scenario 4-7. Explain why an experiment involving 600 men and 500 women is preferable to one involving 60 men and 50 women. 8. Use Scenario 4-7. Assume that 600 men and 500 women suffering from high blood pressure are available for the study. Describe a design for this experiment. Be sure to include a description of how you assign individuals to the treatment groups. 9. Bias is present in each of the following sampling designs. In each case, identify the type of bias involved and state whether you think the sample result obtained is lower or higher than the actual value for the population. (a) A political pollster seeks information about the proportion of American adults who oppose gun controls. He asks an SRS of 1000 American adults: Do you agree or disagree with the following statement: Americans should preserve their constitutional right to keep and bear arms. A total of 910, or 91%, said, Agree (that is, 910 out of the 1000 oppose gun controls). (b) A flour company in Minneapolis wants to know what percent of local households bake at least twice a week. A company representative calls 500 randomly-selected households during the daytime and finds that 50% of those who responded bake at least twice a week. 2

3 Name: Multiple Choice Identify the choice that best completes the statement or answers the question. 1. An experiment to measure the effect of giving growth hormones to girls affected by Turner s Syndrome was carried out recently in Vancouver. All 34 girls in the study were given the growth hormone and their heights were measured at the time the hormone was given and again one year later. No measurements were made on their final adult heights. Which of the following is not a problem with this experiment: A. There was no blinding. B. There was no control group. C. Nonresponse bias D. There was insufficient attention to the placebo effect. E. Because final heights were not measured, it is impossible to tell if the hormone affected final height or only accelerated growth and made no difference to final height. 2. The following numbers appear in a table of random digits: A scientist will be measuring the total amount of leaf litter in a random sample ( n = 5) of forest sites selected without replacement from a population of 45 sites. The sites are labeled 01, 02,..., 45 and she starts at the beginning of the line of random digits and takes consecutive pairs of digits. Which of the following is correct? A. Her sample is 38, 25, 02, 38, 22 B. Her sample is 38, 68, 35, 02, 22 C. Her sample is 38, 35, 27, 28, 08 D. Her sample is 38, 65, 35, 02, 79 E. Her sample is 38, 35, 02, 22, 40 3

4 Name: 3. A civil engineer is testing the reliability of traffic signal controllers produced by two different companies. He has 20 sets of controllers from each company, and he has been given clearance to install them at 40 different intersections in the city. He randomly assigns the controllers from company A to 20 intersections and the controllers from company B to the other intersections. The most important reason for this random assignment is that A. randomization is a good way to create two groups of 20 intersections that are as similar as possible, so that comparisons can be made between the two groups. B. randomization eliminates the impact of any confounding variables. C. randomization makes the analysis easier since the data can be collected and entered into the computer in any order. D. randomization ensures that the study is double-blind. E. randomization reduces the impact of outliers. 4. To test the effects of a new fertilizer, 100 plots were divided in half. Fertilizer A is randomly applied to one half, and B to the other. This is A. an observational study. B. a matched pairs experiment. C. a completely randomized experiment. D. a block design, but not a matched pairs experiment. E. impossible to classify unless more details of the study are provided. 5. An airline that wants to assess customer satisfaction chooses a random sample of 10 of its flights during a single month and asks all of the passengers on those flights to fill out a survey. This is an example of a A. multistage sample. B. stratified sample. C. cluster sample. D. simple random sample. E. convenience sample. 4

5 Name: 6. According to the 1990 census, those states with an above-average number of people X, who fail to complete high school tend to have an above average number of infant deaths, Y. In other words, there is a positive association between X and Y. The most plausible explanation for this is A. X causes Y. Programs to keep teens in school will help reduce the number of infant deaths. B. Y causes X. Programs that reduce infant deaths will ultimately reduce high school dropouts. C. Lurking variables are probably present. For example, states with large populations may have both larger numbers of people who don t complete high school and more infant deaths. D. Both of these variables are directly affected by the higher incidence of cancer in certain states. E. The association between X and Y is purely coincidental. 7. Eighty volunteers who currently use a certain brand of over-the-counter allergy medication have been recruited to participate in a trial of a new allergy medication. The volunteers are randomly assigned to one of two groups. One group continues to take their current medication, the other group switches to the new experimental medication. Each is asked after two weeks if their allergy symptoms are worse, better, or about the same as they were at the start of the study. Which of the follow best describes a conclusion that can be drawn from this study? A. We can determine whether the new drug reduces symptoms more than the old drug for anyone who suffers from allergies. B. We can determine whether the new drug reduces symptoms more than the old drug for the subjects in the study. C. We can determine whether the allergies sufferers symptoms improved more with the new drug than with the old drug, but we can t establish cause and effect. D. We cannot draw any conclusions, since the all the volunteers were already taking the old drug when the experiment started. E. We cannot draw any conclusions, because there was no control group. 8. The Hemlock Woolly Adelgid is an insect that has accidentally been released in Eastern U.S. forests from Asia. Since it has no natural enemies in the U.S., it is spreading rapidly. A forester studying the abundance of the insect in southern Vermont wants to determine if it has spread that far north. He randomly selects 200 hemlock trees in a large Vermont forest and finds that 46 of them show signs of damage from this insect. It would be appropriate to generalize the results of the study to A. all hemlock trees in southern Vermont. B. all trees in southern Vermont. C. the 200 hemlock trees that were randomly selected D. all hemlock trees in the United states. E. all hemlock trees in the forest from which the 200 trees were selected. 5

6 Name: 9. A sample of student opinion at a Big Ten university selects an SRS of 200 of the 30,000 undergraduate students and a separate SRS of 100 of the 5,000 graduate students. This kind of sample is called a A. simple random sample. B. simple random sample with blocking. C. multistage random sample. D. stratified random sample. E. random cluster sample. 10. The Texas experiment described in the previous question A. has one factor: the type of AP Statistics curriculum a student is assigned to. B. has two factors: the type of AP Statistics curriculum and the teacher a student is assigned to. C. has two factors: the standard curriculum and one with the hands-on approach. D. has three factors: the type of AP Statistics curriculum, the teacher, and the class a student is assigned to. E. has three factors: the standard curriculum, the hands-on approach, and the teacher a student is assigned to. 11. An article in the student newspaper of a large university had the headline A's swapped for evaluations? The article included the following. According to a new study, teachers may be more inclined to give higher grades to students, hoping to gain favor with the university administrators who grant tenure. The study examined the average grade and teaching evaluation in a large number of courses in order to investigate the effects of grade inflation on evaluations. I am concerned with student evaluations because instruction has become a popularity contest for some teachers, said Professor Smith, who recently completed the study. Results showed that higher grades directly corresponded to a more positive evaluation. Which of the following would be a valid conclusion to draw from the study? A. A teacher can improve his or her teaching evaluations by giving good grades. B. A good teacher, as measured by teaching evaluations, helps students learn better, resulting in higher grades. C. Teachers of courses in which the mean grade is above average apparently tend to have above-average teaching evaluations. D. Teaching evaluations should be conducted before grades are awarded. E. All of the above. 6