If the coefficient of correlation r = −.81,the standard deviations of x and y are 20 and 25,respectively,then cov(x,y)must be −405.0.

Question

Quizplus · Accepted Answer

We can use the formula for covariance to solve for cov(x,y):

cov(x,y) = r * (std dev of x) * (std dev of y)

Substituting the given values:

cov(x,y) = (-0.81) * 20 * 25

cov(x,y) = -405

Therefore, the statement is true and the answer is A.

If the Coefficient of Correlation R = −