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8. A researcher observes that, on average, the number of divorces in cities with Major League 4. A researcher for a consumer products company is field festing a new formula for laundry detergent. Baseball teams is larger than in cities without Major League Baseball teams. Which of the He has contracted with 60 families, each with two children, who have agreed to test the product. following is the most plausible explanation for this observed association? He randomly assigns 30 families to the group that will use the new formula and 30 to the group (a) The presence of a Major League Baseball team causes the number of divorces to rise (perhaps that will use the company's current detergent formula. The most important reason for this random assignment is that husbands are spending too much time at the ballpark). (n) randomization makes the analysis easier since the data can be collected and entered into the (b) The high number of divorces is responsible for the presence of Major League Baseball teams (more single men means potentially more fans at the ballpark. making it attractive for an owner computer in any order. (b) randomization eliminates the impact of any confounding variables. to relocate to such cities). (c) randomization is a good way to create two groups of 30 families that are as similar as possible, (c) The association is due to confounding (Major League teams tend to be in large cities with more so that comparisons can be made between the two groups. people, hence a greater number of divorces). (d) randomization ensures that the study is double-blind. (d) The association makes no sense. since many married couples go to the ballpark together. (e) randomization reduces the impact of outliers. (c) The association is purely coincidental. It is implausible to believe the observed association could be anything other than accidental. 5. To test the effect of music on productivity. a group of assembly line workers are given portable mp3 players to play whatever music they choose while working for one month. For another month, 9. Control groups are used in experiments in order to accomplish which one of the following? they work without music. The order of the two treatments for each worker is determined (a) Limit the effects of variables other than the explanatory variable on the outcome. randomly. This is (b) Control the subjects of a study to ensure that all participate equally. (@) an observational study. (c) Guarantee that someone other than the investigators, who have a vested interest in the outcome. (b) a matched pairs experiment. controls how the experiment is conducted. (c) a completely randomized experiment. (d) Achieve a proper and uniform level of randomization. (d) a block design, but not a matched pairs experiment. (c) Reduce variability in results. (c) impossible to classify unless more details of the study are provided. 10. A survey is to be administered to recent graduates of a certain nursing school in order to compare 6. A survey was done in the town of Mechanicsville to estimate the proportion of cars that are red and the starting salaries of women and men. For a random sample of graduates, three variables are to be made by companies based in Japan. A simple random sample of 25 cars from a parking lot at Lee- recorded: sex, starting salary. and area of specialization. Which of the following best describes a Davis High School was taken. Which of the following statements is correct? conclusion that can be drawn from this study? (a) Since this is a simple random sample. it should be representative of all the cars in (n) Whether being female causes graduates of this nursing school to have lower (or higher) starting Mechanicsville. salaries than males. (b) If a simple random sample of 15 cars were taken, we would expect the same amount of than males. (b) Whether being female causes graduates in this sample to have lower (or higher) starting salaries variability in the proportion of red cars as we would with a sample of 25 cars. (c) An alternative method for getting a representative sample would be to select the 25 cars closest (c) Whether choosing a certain area of specialization causes females graduates of this nursing to a specified location. such as the entrance to the gymnasium. school to have lower (or higher) starting salaries than males. (d) A different team doing the sampling independently would probably obtain a slightly different answer for their sample proportion. school. (d) Whether there is an association between sex and starting salary among graduates of this nursing (c) The results would be the same regardless of the time of day that the sample is taken. (e) Whether there is an association between sex and starting salary at all nursing schools. 7. A nutritionist wants to study the effect of storage time (6, 12, and 18 months) on the amount of vitamin C' present in freeze dried fruit when stored for these lengths of time. Six fruit packs were randomly assigned to each of the three storage times. The treatment. experimental unit. and response are respectively: (a) A specific storage time. amount of vitamin C. a fruit pack (b) A fruit pack. amount of vitamin C. a specific storage time (c) Random assignment. a fruit pack, amount of vitamin C (d) A specific storage time, a fruit pack, amount of vitamin C (c) A specific storage time, six fruit packs, amount of vitamin C Page 5 1 5