Std DeviationThe Std Deviation study plots the size of the standard deviation of the data over the given period. The standard deviation is the most common measure of statistical dispersion. Simply put, standard deviation measures how spread out the values in a data set are. More precisely, it is a measure of the average distance of the data values from their mean. If the data points are all close to the mean, then the standard deviation will be low (closer to zero). If many data points are very different from the mean, then the standard deviation is high (further from zero). If all the data values are equal, then the standard deviation will be zero. There is no maximum value, although it will be limited by the data set.
The standard deviation (for a variable X) is defined as: