Statistics
Standard Deviation Calculator
Paste your numbers, straight from an Excel column if you like, and choose sample or population. Use sample when your data is a subset of a bigger group, which is most of the time.
Your result will appear here.
How it's calculated
Find the mean, subtract it from each value, square the results and add them up. Divide by n − 1 for a sample or n for a population to get the variance. The standard deviation is the square root of the variance.
Dividing a sample by n − 1 corrects for the fact that a sample tends to sit closer to its own mean than to the true population mean.
s = √( Σ(x − x̄)² ÷ (n − 1) )
How to do it in Excel
=STDEV.S(A2:A8)- Sample standard deviation.
=STDEV.P(A2:A8)- Population standard deviation.
=VAR.S(A2:A8)- Sample variance. VAR.P gives the population version.