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The life in hours of a 75-watt light bulb is known to be normally distributed with...

The life in hours of a 75-watt light bulb is known to be normally distributed with σ = 22 hours. A random sample of 20 bulbs has a mean life of x = 1014 hours. Suppose that we wanted the total width of the two-sided confidence interval on mean life to be six hours at 95% confidence. What sample size should be used? Round up the answer to the nearest integer.

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TOPIC:Finding the required sample size for the given confidence level.

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