An informal discussion of why we divide by n-1 in the sample variance formula. I give some motivation for why we should divide by something less than n, and (casually) discuss the concept of degrees of freedom (in the context of the sample variance). I have another video with a mathematical proof that dividing by n-1 results in an unbiased estimator of the population variance, available at    • Proof that the Sample Variance is an ...  .