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StatisticsStandard Deviation
By Sitraka Forler · Lecturer, Durham Business SchoolUpdated 13 September 2026 About this site
Average spread of values around the mean.
Standard deviation (σ) quantifies dispersion. In finance it is the main measure of volatility. A daily return std dev of 1.5% annualises to about 24% - roughly in line with an equity index in a normal year.
Example
std = returns.std() ann_vol = std * np.sqrt(252)