Arithmetic Mean 

Definition:

The sum of the numerical values of each and every observation, that is divided by the total number of observations is equal to “Arithmetic Mean”. 

Arithmetic Mean is also called average or mean.

The Arithmetic Mean or mean or average is defined 
as,
 
Symbol:             X  = (𝚺x_i)/n

X = Mean

𝚺 = Addition of all number

x_{i =} All of value of X

n = Number of observations, or Number of items are there.

                          Sum of observations
        Mean =   ______________________ 
                         Number of observations

How to calculate mean

Example: What is the mean of  1, 2, 5, and 4.

                          Sum of observations
      Mean =   ______________________ 

                         Number of observations

                            1 + 2 + 5 + 4
         mean =      ________________
                            4   

                 mean  =   12/4

                 mean   =  3

There are two steps to calculate mean 

1.  Step

Add all numbers.

2.  Step

 Divide by how many numbers are there.

Example: What is the mean of  1, 4, 5, 3, and 7.

 1.  Step 

 Add all numbers 

1 + 4 + 5 + 3 + 7 

= 20

2.  Step  

Divide by how many numbers are there.

There are total numbers are 5 so, 20 divide by 5

values put in the formula

                          Sum of observations
      Mean =   ______________________ 

                         Number of observations

                    mean   = 20/5

                     mean  = 5