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A researcher obtained estimates for the mean age, μ, of all U.S. millionaires. He randomly selected...

A researcher obtained estimates for the mean age, μ, of all U.S. millionaires. He randomly selected 49 U.S. millionaires and found that the mean age is 57.42 years. Assume that the standard deviation of ages of all U.S. millionaires is 12.0 years.

(i) Determine the margin of error, E, for a 90% confidence interval.

(ii) Determine the sample size required to have a margin of error of 4.2 years with a 98% confidence level.

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