46Correlation from covariance

$\displaystyle \mathrm{Cov}(X, Y) = 6$, $\displaystyle \sigma_X = 2$ and $\displaystyle \sigma_Y = 5$. Find the correlation of $\displaystyle X$ and $\displaystyle Y$.

Correlation is covariance divided by the product of the standard deviations: ρ = 6/(2×5) = 6/10 = 0.6. This is boxed; it's a fairly strong positive correlation, and lies correctly between −1 and 1.