Standard Deviation (Volatility)
Standard Deviation measures the degree of variation/uncertainty of returns around the mean/average return. The higher the volatility of the investment returns, the higher the standard deviation. That is why the standard deviation is often used as a measure of risk.
Standard Deviaiton is available in different variants, e.g. calculated for last 3,6 months, annualized, or for different yearly periods.
TopSheets uses SAMPLE standard deviation as opposed to POPULATION standard deviation. Sample standard deviation is the industry standard.