Standard deviation is a tool which helps measure the total risk that is associated with a fund. It helps to measure the extent to which the fund’s returns vary across its average returns. These returns can be calculated by a change in the percentage of the net asset value (NAV), which can be calculated over different time frames varying from daily, weekly, monthly, quarterly, or annual periods. If the standard deviation is high, then it signifies that your periodic returns are undergoing fluctuation, thereby signifying risks involved in the investment. Low standard deviation indicates that your periodic returns are undergoing fluctuations that are closer to the expected average returns, thereby implying a lower probability of loss on your investments. Hope this helps!