Why n-1 Instead of n
Two panels: seeing one giant alien tells you nothing about the spread of alien heights, but seeing two lets you start estimating, which is the intuition behind dividing by n-1.
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Cartoon by Ben Orlin, Math with Bad Drawings. https://cartoons.mathwithbaddrawings.com/2017-11-30-why-n-1-instead-of-n/ (CC BY-NC 4.0)Transcript
[Title] "Why, When Estimating Population Variance from a Sample, You Use n-1 Instead of n"
[n = 1] A: "Wow! An alien! 50 feet tall! I wonder what the variance of alien heights is..." B: "Beats me." Caption: "no way to estimate variance"
[n = 2] A: "Wow! A 50-foot alien and a 57-foot alien! I wonder what the variance is..." B: "Well, I've got a guess..." Caption: "possible to estimate variance"