: <p>

x y <p>

0 0
 1 1
 -1 1
 2 4
 -2 4 <p>

Notice that the y-value of each point is the square of its x-
value. Thus the y-value of a point is completely determined by
its x-value.  If correlation measured association in general, the
correlation coefficient of this scatter diagram would have to
reflect this perfect association. It would have to have a value
of -1 or 1.  Instead, the value of the correlation coefficient is
equal to <p>

a.  -0.5 <p>

b.    0 <p>

c.   0.5 <p>

d.  -0.75
 
 e.   0.75 <p>