Standard Deviation

The standard deviation falls under descriptive statistics and is the most frequently used measure of variability. It represents the average amount of variability in a set of scores. More simply put, it's the average amount of distance from the mean.

The purpose of standard deviation is so that we can understand how spread out a data set is. A high standard deviation implies that, on average, data points are all pretty far from the average and looks spread out. A low standard deviation means most points are very close to the average.

References