It is the average of a collection of numbers obtained by dividing the sum of those numbers by amount of those numbers.

The arithmetic mean is defined by the following expression:

 

Example:            Given the following marks in a class of 30 students, in two subjects, let's calculate the mean in x and y, checking whether there is correlation in foreign language learning.

 

Literature (x)	3,7,8,7,5,2,5,9,5,4,3,5,3,6,3,8,5,7,7,6,2,4,9,4,9,7,6,7,1,7
Foreign language (y)	2,6,10,6,4,2,5,9,5,5,2,4,1,5,1,10,4,7,8,4,2,5,9,5,9,8,5,7,0,7