Standard Deviation
![Bell curve with red in the middle, green in the opposite middle layers, and blue in the opposite outside layers](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/styles/full_width/public/media/images/standard_dev.gif?itok=SOkmdeTy)
Detailed Description
The standard deviation is how much a set of data is different from the curve it should make when plotted on a graph. Or, the square root of the average of the squares of deviations about the mean of a set of data. Standard deviation is a statistical measure of spread or variability.