why is standard deviation often used more than variance 
standard deviation is the square root of variance it is sometimes more useful since taking the square root removes the units from the analysis this allows for direct comparisons between different things that may have different units or different magnitudes for instance to say that increasing x by one unit increases y by two standard deviations allows you to understand the relationship between x and y regardless of what units they are expressed in the bottom linevariance measures variability or how far numbers in a data set diverge from the mean it is used by various professionals including data analysts mathematicians scientists statisticians and investors the latter two use variance to determine whether to buy sell or hold securities for example if an investment has a greater variance it could be considered more volatile and risky 