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# Confidence interval of proportion

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4. An automobile manufacturer gives a 5 year/60,000 mile warranty on its drive train. Historically, 7% of this manufacturer's cars have required service under this warranty. Recently, a design team proposed an improvement that should extend the drive train's life. A random sample of 200 cars underwent 60,000 miles of road testing, in which tests the drive train of 12 cars failed.

a. Conduct the most appropriate hypothesis test using a 0.05 significance level.
b. Construct a 95% confidence interval for the true proportion of automobiles with drive trains that fail.

https://brainmass.com/statistics/confidence-interval/confidence-interval-proportion-82777

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An automobile manufacturer gives a 5 year/60,000 mile warranty on its drive train. Historically, 7% of this manufacturer's cars have required service under this warranty. Recently, a design team proposed ...

#### Solution Summary

The expert examines confidence intervals of proportions.

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