Example:

Find the standard deviation of the following set of numbers

68, 40, 16, 22, 27

1. Find the mean
   Mean = 34.6
   Click here to see how to find the mean 
    

2. Subtract the mean from every single number in the number set
   68-34.6 = 33.4
   40-34.6 = 5.4
   16-34.6 = 18.6
   22-34.6= -12.6
   27-34.6 = -7.6
    

3. Square each difference
   33.4^2 = 1556.56
   5.4^2 = 29.16
   -18.6^2 = 345.56 
   -12.6^2 = 158.76
   -7.6^2 = 57.76
    

4. Add all the squared differences
   1556.56 + 29.16 + 345.56 + 158.76 + 57.76 = 1707.2
    

5. Divide by n – 1
   1707.2 / (5 - 1) = 426.80 <--- This is the variance!
    

6. Square root the quotient