To Investigate the Relationship Between Yield of Potatoes, Y, and Level

To investigate the relationship between yield of potatoes, y, and level of fertilizer application, x, a researcher divides a field into eight plots of equal size and applies differing amounts of fertilizer to each. The yield of potatoes (in pounds) and the fertilizer application (in pounds) are recorded for each plot. The data are as follows:
$\begin{array}{l|cccccccc}\hline x & 1 & 1.5 & 2 & 2.5 & 3 & 3.5 & 4 & 4.5 \\\hline y & 25 & 31 & 27 & 28 & 36 & 35 & 32 & 34 \\\hline\end{array}$

Summary statistics yield $S S _ { x x } = 10.5 , S S _ { y y } = 112 , S S _ { x y } = 25$ , and $S S E = 52.476$ . Calculate the coefficient of correlation.