Victory for the ACT Student Text 15e

L ESSON 2 | R ESEARCH S UMMARY • 307 Which hypothesis best explains the observation that the agar plates never appear clear beyond a 2” area surrounding the soaked paper disks? A. The bacteria cannot grow well within 2” of any moist paper disks. B. The antibiotics cannot seep through the agar beyond a distance of 2”. C. At the experimental incubation temperatures used, the two antibiotics interfere with each other’s effectiveness. D. The paper disks can absorb nutrients out of the agar from the distance of 2”. If either Antibiotic I or II could be prescribed for internal use to prevent the spread of Bacterium X infections, which recommendation, based on the experimental results, is appropriate if the cost due to the amount of antibiotic used per dose is the most critical factor (the antibiotics are equal in cost for equal concentrations)? F. Either Antibiotic I or II can be taken at equal cost. G. Antibiotic I would be less expensive. H. Antibiotic II would be less expensive. J. Neither Antibiotic I nor II would be effective in preventing the spread of Bacterium X .

Which of the following results would indicate that the antibiotics being tested have nothing to do with the control of bacterial growth? F. A clear, 2” region was always observed around the disks soaked in water. G. All results remained the same at the two experimental temperatures and at the two antibiotic concentration levels. H. Plates A and B always remained clear. J. The disks soaked in water were not used in the experiments at all. Which statement is supported by the results of Experiment 1 alone? A. Antibiotic I, Antibiotic II, and water are equally effective as inhibitors (preventers) of bacterial growth at 37°C. B. Dry paper disks can be effective in controlling bacterial growth at 37°C. C. The concentration of an antibiotic ƒ› ‹ϐŽ—‡…‡ ‹–• ‡ˆˆ‡…–‹˜‡‡•• ‹ controlling bacterial growth at 37°C. D. Both Antibiotics I and II can inhibit bacterial growth at 37°C. The results of both Experiment 2 and Experiment 3 lead to which of the following conclusions? F. Antibiotics I and II have similar effects on bacterial growth, regardless of concentrations. G. Antibiotic II and water have similar effects on bacterial growth, regardless of concentrations. H. The effectiveness of Antibiotic I at 22°C depends on its concentration. J. The effectiveness of Antibiotic II at 22°C depends on its concentration.

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The Cambridge Edge How can you recognize a Research Summary item? Here are some sample items to help you recognize what these questions ask: 1. Identify the difference in the experimental design of the two experiments. 2. Predict an outcome based on the results of Experiment 2. 3. Predict the outcome of Experiment 1 when one of the variables is altered. 4. Identify an assumption of Experiment 2 based on the results. 5. Identify a conclusion supported by the results of Experiment 1. 6. Select an experiment that should be conducted in order to test another hypothesis. 7. Identify a hypothesis that was

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investigated in Experiment 1.