What is standard deviation

Standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the values are spread out over a wider range.

For example, if a class of students has test scores with a low standard deviation, it means most students scored very close to the average score. If the standard deviation is high, it means the scores are more spread out, with some students scoring much higher and some much lower than the average.