Final answer:
The standard deviation measures variability and the average deviation of scores about the mean.
Step-by-step explanation:
The standard deviation measures the variability and the average deviation of scores about the mean. It provides a numerical measure of the overall amount of variation in a data set. When the standard deviation is small, it means the data values are concentrated close to the mean and there is little variation. When the standard deviation is large, it means the data values are more spread out from the mean, indicating more variation.