# Confidence interval for a mean

Cotinine Levels of Smokers When people smoke, the nicotine they absorb is converted to cotinine, which can be measured. A sample of 40 smokers has a mean cotinine level of 172.5. Assume that the population standard deviation is known to be 119.5, find a 90% confidence interval estimate of the mean cotinine level of all smokers. What aspect of this problem is not realistic?

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#### Solution Summary

This solution finds and interprets a confidence interval for the mean cotinine level of smokers.

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