5608. A sample from a large batch of electric lamps contains 100 lamps. The average lamp burning time of the sample turned out to be 1000 hours. Find, with a reliability of 0.95, a confidence interval for the average burning time of the lamps of the entire batch, if it is known that the standard deviation of the lamp burning time is σ=40 h.

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