Problem N5611 probability theory confidence interval

Problem N5611 probability theory confidence interval

5611. From a large batch of light bulbs, a sample of 100 light bulbs was made for testing for burning duration. The average burning time was found to be 300 hours. Assuming that the light bulb burn time is normally distributed with a standard deviation of 35 hours, find the confidence interval for M(x) with a reliability of 0.95

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Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)