:4. A scatter diagram contains five points. Four of them lie on a straight line. The fifth one does not lie on that line. Let r be the correlation coefficient of the scatter diagram. One of the following is true. Which one?
a. Since 80% of the points lie on a straight line, r has to equal 0.8 or -0.8.
b. r has to equal -1
c. r has to equal 1
d. r is either 1 or -1, but we can't tell which.
e. r doesn't need to be 0.8 or -0.8, but it certainly is neither 1 nor -1.