Problem N5607 probability theory confidence interval

Problem N5607 probability theory confidence interval

5607. From a large batch of electric lamps, a sample of 100 lamps was made for testing for burning duration. The average burning time turned out to be 3000 hours. Assuming that the burning time has a normal distribution with a standard deviation σ=35 h, find the confidence interval for the mathematical expectation a with the reliability γ=0.95.

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