The graph below plots the values of y for different values of x:
plot the ordered pairs :
1, 3 and 2, 4 and 3, 9 and 4, 7 and 5, 2 and 6, 18
which correlation coefficient best matches the data plotted on the graph?
0.5
0.8
0.9
1.0

Mean of x = (1 + 2 + 3 + 4 + 5 + 6) / 6 = 21/6 = 3.5
mean of y = (3 + 4 + 9 + 7 + 2 + 18) / 6 = 43/6 = 7.167
∑(xi - x(bar))((xi - x(bar)) = [(1 - 3.5)(3 - 7.167) + (2 - 3.5)(4 - 7.167) + (3 - 3.5)(9 - 7.167) + (4 - 3.5)(7 - 7.167) + (5 - 3.5)(2- 7.167) + (6 - 3.5)(18 - 7.167) = [-2.5(-4.167) + (-1.5)(-3.167) + (-0.5)(1.833) + 0.5(-0.167) + 1.5(-5.167) + 2.5(10.833)] = 10.4175 + 4.7505 - 0.9165 - 0.0835 - 7.7505 + 27.0825 = 33.2305
∑(xi - x(bar))^2 = (-2.5)^2 + (-1.5)^2 + (-0.5)^2 + (0.5)^2 + (1.5)^2 + (2.5)^2
 = 6.25 + 2.25 + 0.25 + 0.25 + 2.25 + 6.25 = 17.5
∑(yi - y(bar))^2 = (-4.167)^2 + (-3.167)^2 + (1.833)^2 + (-0.167)^2 + (-5.167)^2 + (10.833)^2 = 17.3639 + 10.0299 + 3.3599 + 0.0279 + 26.6979 + 117.3539 = 174.8334

correlation coefficient = 33.2305/sqrt(17.5 x 174.8334) = 33.2305/sqrt(3059.5845) = 33.2305/55.3135 = 0.6

O.5. you dont need to do all the fancy math