7.125 The lightbulbs used to provide exterior lighting for a large office building have an average lifetime

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7.125 The lightbulbs used to provide exterior lighting for a large office building have an average lifetime of 700 hours. If length of life is approximately normally distributed with a standard deviation of 50 hours, how often should all the bulbs be replaced so that no more than 20% of the bulbs will have already burned out?

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Introduction To Statistics And Data Analysis

ISBN: 9780840054906

4th Edition

Authors: Roxy Peck, Chris Olsen, Jay L. Devore

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