Standard deviation is a measures of the amount of variation from the average or mean. Deviation means how far a number is from the average. The more spread apart the data, the higher is the deviation.
To calcualate Standard Deviation:
Sample number: 1, 2, 3, 4, 5
(1 + 2 + 3 + 4 + 5) / 5 = 3
((1 - 3)² + (2 - 3)² + (3 - 3)² + (4 -3)² + (5 - 3)²) / 5 = 2
((1 - 3)² + (2 - 3)² + (3 - 3)² + (4 -3)² + (5 - 3)²) / (5 - 1) = 2.5
Whole Population:
σ = √Σ(x - y)² / z Where: σ = Standard Deviation x = each value in the population y = mean of the values z = number of values (population size)
Sample Population:
σ = √Σ(x - y)² / (z - 1) Where: σ = Standard Deviation x = each value in the population y = mean of the values z = number of values (sample size)