The Composition of the Earth's Atmosphere May Have Changed Over

question 11

Essay

The composition of the earth's atmosphere may have changed over time. One attempt to discover the nature of the atmosphere long ago involved measuring the gas trapped in bubbles inside ancient amber. Amber is tree resin that has hardened and been trapped in rocks. Measurements on nine amber specimens from the late Cretaceous era (95 to 65 million years ago) give the following percentages of nitrogen: 63.4, 65.0, 64.4, 63.3, 54.8, 68.5, 60.8, 59.1, 51.0 Assume that it is reasonable to regard these trapped gas bubbles as a random sample of bubbles from the Cretaceous atmosphere.
a) Construct and interpret a 95% confidence interval for the mean percentage of nitrogen in the Cretaceous atmosphere.
b) The mean percentage of nitrogen in the atmosphere today is about 79%. Based on the confidence interval from part (a), do you think that the percentage of the atmosphere that is nitrogen has changed from the late Cretaceous era? Explain.

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