Index of dispersion - Wikipedia
https://en.wikipedia.org/wiki/Index_of_dispersionIn probability theory and statistics, the index of dispersion, dispersion index, coefficient of dispersion, relative variance, or variance-to-mean ratio (VMR), like the coefficient of variation, is a normalized measure of the dispersion of a probability distribution: it is a measure used to quantify whether a set of observed occurrences are clustered or dispersed compared to a standard statistical model.
Approximations for Mean and Variance of a Ratio
stat.cmu.edu/~hseltman/files/ratio.pdfApproximations for Mean and Variance of a Ratio Consider random variables Rand Swhere Seither has no mass at 0 (discrete) or has support [0;1). Let G = g(R;S) = R=S. Find approximations for EGand Var(G) using Taylor expansions of g(). For any f(x;y), the bivariate first order Taylor expansion about any = ( x; y) is f(x;y) = f( )+f 0 x ( )(x x ...