Question

Co-efficient of correlation between the variables X and Y is 0.3 and their covariance is 12. The variance of X is 9, find the standard deviation of Y.

Answer 1

Given r_xy = 0.3, cov(x,y) = 12, Vx = 9

σ = 3
r_xy = `(cov(x,y))/(σ_x . σy)`

0.3 = `12/(3 . σ_y)`

0.3 = `4/σ_y`

`σ_y = 4/0.3`

`σ_y = 40/3`

`σ_y = 13.33`