Free Standard Deviation Calculator
Calculate the population standard deviation of three values. Standard deviation measures how spread out numbers are from the mean.
Std Dev
8.164966
Std Dev Sample10.000000
Variance Pop66.666667
Mean20.0000
How to Calculate Standard Deviation
Formula (Population)
σ = √[ Σ(xᵢ - μ)² / N ]
Steps
1. Find the mean (μ) of the data set 2. Subtract the mean from each value and square the result 3. Find the average of those squared differences 4. Take the square root
For a sample standard deviation, divide by (N-1) instead of N.
Example Calculation
Find the standard deviation of 10, 20, and 30.
- 01Mean = (10 + 20 + 30) / 3 = 20
- 02Squared differences: (10-20)² = 100, (20-20)² = 0, (30-20)² = 100
- 03Variance (population) = (100 + 0 + 100) / 3 = 66.6667
- 04Standard Deviation = √66.6667 ≈ 8.1650
Frequently Asked Questions
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