Math
Standard Deviation Calculator
Calculate population and sample standard deviation, variance, and summary statistics for your data set.
Mean
21.0000
Population Std Dev
6.0000
Sample Std Dev
6.4807
Count
7
Population Variance
36.0000
Sample Variance
42.0000
Summary Statistics
Min
12.00
Max
30.00
Range
18.00
Sum
147.00
Frequently asked questions
What's the difference between population and sample standard deviation?
Population standard deviation uses all data points (divide by N). Sample standard deviation uses a subset and divides by N-1 (Bessel's correction) to get an unbiased estimate of the population.
What does standard deviation tell me?
Standard deviation measures how spread out numbers are. A low SD means numbers cluster near the mean. A high SD means numbers are spread over a wider range.
When should I use sample vs population?
Use population when your data includes every member of a group. Use sample when you have a subset and want to estimate the population parameter.
What's the relationship between variance and standard deviation?
Standard deviation is the square root of variance. Variance is expressed in squared units, while standard deviation is in the original units of the data, making it easier to interpret.
Compute standard deviation, variance, and summary statistics for any data set. Choose between population and sample formulas depending on your data.