Proof that the Sample Variance is an Unbiased Estimator of the Population Variance

A proof that the sample variance (with n-1 in the denominator) is an unbiased estimator of the population variance. In this proof I use the fact that the sampling distribution of the sample mean has a mean of mu and a variance of sigma^2/n. If you need that to be shown as well, I show that in this video:    • Deriving the Mean and Variance of the Samp...  .