: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.