The standard deviation of the rate of return measures the deviation of the daily rate of return of the fund from the average rate of return, which is used to measure the fluctuation of the fund's income. It is obtained by calculating the actual rate of return MINUS the expected rate of return, then multiplying each deviation square by the probability corresponding to the actual rate of return, and adding the standard deviation of the variance of the total rate of return.

Generally speaking, the greater the standard deviation of the fund, the greater the corresponding risk.