The population variance is the value of variance that is calculated from the population data. Whereas sample variance is the variance value calculated from the sample data. The population variance formula is σ2 = ∑(xi - μ)2 / N. The sample variance is the replacement of N by N-1 in population variance. So, the formula of sample variance is s2 = ∑(xi - x̄)2 / (N - 1).