Find the observed significance level for the test described in Example 7.8. Interpret the result.

Example 7.8

A major car manufacturer wants to test a new engine to determine whether it meets new air pollution standards. The mean emission m of all engines of this type must be less than 20 parts per million of carbon. Ten engines are manufactured for testing purposes, and the emission level of each is determined. The data (in parts per million) are listed in Table 7.5.

Do the data supply sufficient evidence to allow the manufacturer to conclude that this type of engine meets the pollution standard? Assume that the production process is stable and the manufacturer is willing to risk a Type I error with probability α = .01.

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Table 7.5 Emission Levels for Ten Engines 15.6 16.2 22.5 20.5 16.4 19.4 19.6 17.9 12.7 14.9