Standard Deviation

Abstract The standard deviation is a measure of the variability of a set of scores and is defined in relationship to the average of the scores. The average of a set of scores is called the mean. The standard deviation is a measure of how far the scores vary from their mean. If all the scores in a set of data are close to the mean, the standard deviation is small. If all the scores in a set of data are far away from the mean, the standard deviation is large.