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

8-50.

Scientists consider the average growth rate of kelp (a sea plant) to be an indicator of the health of marine plants. They also consider the average weight (mass) of crabs that live in kelp beds to be an indicator of the health of the marine animals. But they want to know if there is an association between the health of sea plants (kelp) and the health of sea animals (crab).

Marine biologists collected data from different parts of the world and created the following 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 the health of sea plants and the health of sea animals? Homework Help ✎

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?