You like to go fishing off a bridge on a quiet back road. Your father showed you this special spot and he always use to say that when cars go over the bridge it scares the fish away and you catch less fish. You decide to test the theory by counting the number of fish caught per hour and the number of cars that go over the bridge per hour while you are fishing. The data looks as follows:

# of fish/hour # of cars/per hour?

11 15

8 6

9 5

13 10

4 3

6 6

What is the correlation coefficient between the two variables?