Standard Deviation Calculator
Compute standard deviation, variance, and mean for a data set.
Standard deviation (sample)
1.8708
Variance
3.5
Mean
5.5
Count
6
Spread around the mean
Standard deviation measures typical distance from the average. In roughly normal data, about 68% of values sit within one SD of the mean and 95% within two — which is why it anchors everything from test scores to quality control.
Sample vs. population
Dividing by n − 1 (Bessel's correction) compensates for the fact that a sample's own mean understates true spread. Use population mode only when your numbers are the entire group of interest, not a sample from it.
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