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Standard Deviation Calculator
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Enter a list of numbers to get the mean, variance, and standard deviation.
| Count (n) | 8 |
| Mean | 18 |
| Variance | 24 |
| Standard Deviation | 4.898 |
Population vs. Sample Standard Deviation
Standard deviation measures how spread out a set of numbers is from its mean. Population standard deviation is used when your data represents the entire group you care about; sample standard deviation is used when your data is only a subset drawn from a larger population, and it divides by n − 1 instead of n to correct for that extra uncertainty.
σ = √( Σ(x − μ)² ÷ N )
Population standard deviation - μ is the mean, N is the count
s = √( Σ(x − x̄)² ÷ (n − 1) )
Sample standard deviation - x̄ is the sample mean, n is the sample size