Work out sample standard deviation instantly with clear inputs, formula shown and shareable results.
The sample standard deviation divides the sum of squared deviations by n − 1 rather than n. That Bessel correction compensates for using the sample mean instead of the unknown population mean, giving an unbiased variance estimate.
Sample standard deviation
s = √[Σ(xᵢ − x̄)² / (n − 1)]
Population standard deviation
σ = √[Σ(xᵢ − μ)² / n]
The mean is 5 and the sample standard deviation is 2.1380899, while the population value is exactly 2.
Use n − 1 when the data is a sample being used to estimate a wider population, and n only when you have the entire population.