### Home > CC3 > Chapter 8 > Lesson 8.2.1 > Problem8-50

8-50.

Scientists consider the average growth rate of kelp (which grows in the sea) and the average mass of crabs that live in kelp beds to be indicators of the health of marine life. But they want to know if there is an association between the growth rates of kelp and the masses of crabs.

Marine biologists collected data from different parts of the world and created the following conditional relative frequency table. They considered the average growth rate of kelp as the independent variable.

 % CRABS Average Mass of Crabs (kg) $\mathbf{< 0.25}$ $\mathbf{0.25 - 0.49}$ $\mathbf{0.50 - 0.75}$ $\mathbf{> 0.75}$ Average Growth Rate of Kelp (cm/day) $\mathbf{< 5}$ $66\%$ $34\%$ $0\%$ $0\%$ $\mathbf{≥ 5}$ $12\%$ $49\%$ $35\%$ $4\%$

Is there an association between growth rates of kelp and the masses of crabs?

Look at the growth rates for both the crabs and the kelp.
When the growth of the kelp is high, what does the growth rate for the crabs look like?
What about when the growth rate for the kelp is low?
What does this tell you about the association?