The MEAN function returns a numeric value that is the arithmetic mean (average) of its arguments. The type of this function
is numeric.
Usage
FUNCTION MEAN ({argument1} ... )
Parameters
argument1

Must be class numeric.

Returned Values
 The returned value is the arithmetic mean of the
argument1 series.
 The returned value is defined as the sum of the
argument1 series divided by the number of occurrences referenced by
argument1.