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📊 Statistics

Standard Deviation Calculator

Free standard deviation calculator. Enter a list of numbers to get mean, median, mode, variance, and standard deviation instantly.

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Standard Deviation Calculator
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Formula

Formula
σ = √(Σ(xᵢ − μ)² ÷ N)
σ is population std dev (divide by N). s is sample std dev (divide by N-1). μ is the mean. Measures how spread out data is from the average.

Frequently Asked Questions

What does standard deviation tell you?+
Standard deviation measures how spread out data is from the mean. Low SD = data clustered near mean. High SD = data spread widely.
When to use population vs sample std dev?+
Population (σ): when you have the complete dataset. Sample (s): when your data is a sample of a larger population. Most real-world use is sample.
What is a good standard deviation?+
It depends on the context. In quality control, lower is better. In finance, higher SD means more volatile (risky) investment.
Is this standard deviation calculator free?+
Yes, completely free with no signup required.

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