5618. 400 pieces were randomly selected from a large batch of electric lamps. to determine the average burning time. The sample average burning time of the lamps turned out to be 1220 hours. Let us find, with a confidence factor γ = 0.997, a confidence interval for the average burning time of an electric lamp over the entire batch, if the standard deviation of the burning time is 35 hours.

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