Standard deviation
A standard deviation is a (slightly messy) statistical calculation that results in a positive number that measures how much the possible results differ from the average result. For those of you who want to know more, it is square root of the weighted averageA calculation using all of the observations of a variable with each observation being assigned a weight. The weight is the relative importance of that observation. Each observation is multiplied b... More of the squares of the differences between each possible result and the mean, where the weights are the probabilities of the various possible results.
