Which of the following is a property of r,the coefficient of correlation?

A) r always lies between 0 and 1.
B) r has no units.
C) If you switch the values of X and Y,the sign of r changes.
D) All of these choices are true.

The coefficient of correlation, denoted as r, is dimensionless, meaning it has no units. This is because it is a standardized measure of the strength and direction of the linear relationship between two variables. Options A and C are incorrect: r actually ranges between -1 and 1, and switching the values of X and Y does not change the sign of r, it remains the same because the correlation measures the strength and direction of a linear relationship irrespective of which variable is considered X or Y.