Most commonly used statistical average -
Arithmetic mean 

It is the most commonly used statistical average.
To calculate mean, add up the values of all individual observation and then divide by the number of observations.
The process of adding together is called summation and is denoted by the sign ∑ or S.
The individual observation is denoted by ŋ
The mean is denoted by the sign X.
Example :-
Mean
Median
Mode
None