Standard deviation is "average distance from the average". That one sentence covers 90% of everything you ever need to remember about it.
What it is
Standard deviation measures how spread out a dataset is around its mean. Small values mean the numbers cluster; large values mean they scatter.
Sample vs population
If your numbers are a sample from a bigger group, divide by n − 1. If they are the whole population, divide by n. The difference is small but real.
Topics:
#Statistics