For example
For the numbers 1, 2, and 3
- The mean is obviously 2, and
- s2 = (1-2)2 + (2-2)2 + (3-2)2 divided by 3 = 0.67
But the scatter of 1 and 3 on either side of 2
- Is obviously 1.00. So, our answer has a bias
- Because it includes the mean value 2
So the realistic answer for variance
- Is given by the formula
s2 = S (x-M)2
N-1
- Where M = Mean and N = Number of readings
- And S means "Sum of all"