Chapter 11 Free Response - same 100 mile course twice; once...

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AP Statistics – Chapter 11: Practice Free Response Exam 1. The composition of the earth’s atmosphere may have changed over time. One attempt to discover the nature of the atmosphere long ago studies the gas trapped in bubbles inside ancient amber. Amber is tree resin that has hardened and been trapped in rocks. The gas in bubbles within amber should be a sample of the atmosphere at the time the amber was formed. Measurement on specimens of amber from the late Cretaceous era (75 to 95 million years ago) gives these percents of nitrogen: 63.4 65.0 64.4 63.3 54.8 64.5 60.8 49.1 51.0 These values appear to be quite lower than the present 78.1% of nitrogen in the atmosphere, but are they significantly lower? a) Carry out a complete test to answer the questions posed. b) Under what conditions is it acceptable to perform the test in part (a) on this data? 2. Automotive researchers wish to determine whether gas mileage is higher when using name brand gas versus discount gas. To test this hypotheses, 10 identical model vehicles drive the
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Unformatted text preview: same 100 mile course twice; once with each type of gas. The amount of fuel used (in gallons) for each type of gas is shown in the table below. Fuel / Car # 1 2 3 4 5 6 7 8 9 10 Name Brand 5.94 5.74 5.24 5.34 5.43 5.84 5.42 5.84 5.87 5.66 Discount 5.82 5.59 5.59 5.64 5.47 5.48 5.50 5.96 5.73 5.75 a) Find a 95% confidence interval for the difference in fuel used ( discount name brand ). b) What does the interval suggest about mileage differences for the two fuel types? 3. Nitrites are often added to meat products as preservatives. In a study of the effect of these chemicals on bacteria, the rate of uptake of a radio-labeled amino acid was measured for a number of cultures of bacteria, some growing in a medium to which nitrites had been added. Here are the summary statistics from this study. Group n x-bar s Nitrite 30 7880 1115 Control 30 8112 1250 Carry out a complete test of the research hypothesis that nitrites decrease amino acid uptake and report your results....
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