The Standard Deviation is a widely used measurement of variability or diversity of a set of measurements. Volitility in the stock market is the Standard Deviation of the value of a stock. Standard Deviation shows how much variation or "dispersion" there is from the "average" (the mean). A low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data is spread out over a large range of values. A useful property of Standard Deviation is that, unlike the variance, it is expressed in the same units as the data. Let's use the vertical position of the sliders below as the data values. Move the sliders up and down.