Answer
There seems to exist a relationship between age and median income (the income increase until 50 years and then it decreases as a man/woman gets older), according to the scatter diagram. But, since it is not a linear relation, we can not use the linear correlation coefficient.
Work Step by Step
The scatter diagram looks like Figure 4 (h) on page 194 with $r\approx0$. This does not imply no relation, but rather the lack of a linear relationship.
