A random sample of 225 measurements is selected from a population, and the sample mean and...

A random sample of 225 measurements is selected from a population, and the sample mean and standard deviation are  and s = 30.0, respectively.

a. Use a 99% confidence interval to estimate the mean of the population, μ.

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b. How large a sample would be needed to estimate μ to within .5 with 99% confidence?

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c. What is meant by the phrase “99% confidence” as it is used in this exercise?

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d. Find a 99% confidence interval for σ2.