Finite population variance ($S^2=(N-1{)}^{-1}{\sum }_i(y_i-\bar{Y}{)}^2$)

For $N>1$, the finite population variance measures spread about the finite population mean. Survey-sampling formulas commonly use denominator $N-1$; the denominator-$N$ version is ${\sigma }_N^2=(N-1)S^2/N$. The normalization must be specified when using a finite population correction.