Problem N5626 probability theory confidence interval

Problem N5626 probability theory confidence interval

5626. A random re-sampling method was used to survey 900 workers of one enterprise, as a result of which the average monthly output of one worker was established - 400 parts. Find with a reliability of 0.95 the boundaries within which the average monthly output of one worker in the general population lies, assuming that the distribution of the monthly output of one worker is normal with a standard deviation of 45 parts.

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