WordNet (r) 3.0 (2006):

arithmetic mean
    n 1: the sum of the values of a random variable divided by the
         number of values [syn: arithmetic mean, first moment,
         expectation, expected value]

The Free On-line Dictionary of Computing (30 December 2018):

arithmetic mean

    The mean of a list of N numbers calculated by
   dividing their sum by N.  The arithmetic mean is appropriate
   for sets of numbers that are added together or that form an
   arithmetic series.  If all the numbers in the list were
   changed to their arithmetic mean then their total would stay
   the same.

   For sets of numbers that are multiplied together, the
   geometric mean is more appropriate.

   (2007-03-20)