MyCalculatorHow it works
We compute the mean, then the average squared deviation from the mean (variance), then take the square root for standard deviation. Sample standard deviation divides by (n−1); population divides by n.
Example
For 2, 4, 4, 4, 5, 5, 7, 9: mean is 5, population standard deviation is 2, sample standard deviation is about 2.14.
Assumptions & limitations
Use sample standard deviation when your numbers are a sample of a larger population (the more common case); use population when your numbers are the entire population.
Frequently asked questions
Which type should I use?
If you're analyzing a sample and want to estimate the whole population's spread, use sample. If your data set is the entire population, use population.