Standard Deviation Calculator
Measure the dispersion of your dataset. Enter numbers separated by commas to find the mean, variance, and standard deviation instantly.
Population (σ)
Sample (s)
Mean ($\mu$)
0
Count ($n$)
0
Variance
0
Std. Deviation
0
Understanding Spread
Standard Deviation tells you how much your data deviates from the average (mean). A low standard deviation means most numbers are close to the mean, while a high value means the data is spread over a wider range.
- Step 1: Calculate the Mean.
- Step 2: Subtract the Mean from each number and square the result.
- Step 3: Calculate the average of those squared differences (Variance).
- Step 4: Take the square root of the Variance (Standard Deviation).
Population vs. Sample? +
Use Population when your dataset represents every single member of a group. Use Sample (which uses $n-1$ in the formula) when your data is just a subset of a larger group. The sample formula is more "conservative" to account for potential bias.
What is the 68-95-99.7 Rule? +
In a normal distribution, about 68% of data falls within 1 standard deviation of the mean, 95% within 2, and 99.7% within 3. This helps identify outliers!
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