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# Confidence Intervals for Normal Distribution

A publisher wants to estimate the mean length of time (in minutes) all adults spend reading newspapers. To determine this estimate, the publisher takes a random sample o 15 people and obtains the results below. From past studies, the publisher assumes o is 1.9 minutes and that the population o times in normally distributed.

10 9 11 9 7 10 11 6 12 7 6 7 10 10 8

Construct the 90% and 99% confidence intervals or the population mean. Which interval is wider? If convenient, use technology to construct the confidence intervals.

The 90% confidence interval is ? (______,______) round to one decimal place

The 99% confidence interval is ? (______,______) round to one decimal place

Which interval is wider?
90% or 99% confidence interval

#### Solution Preview

Solution:

x-bar = sum/15 = 133/15 = 8.87

90% confidence interval will be

(8.87 - ...

#### Solution Summary

The solution determines which confidence interval is wider.

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