Solution: Statistical Analysis with Different Interactions

Let's look at the solution of the previous exercise.

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We first asked if the hatching age and predator treatments affect the length of the tail remaining when the froglets crawl out of the water.

To understand this question, let’s think about the biology of an amphibian. When a tadpole turns into a frog through what we call metamorphosis, one of the changes it goes through is that it resorbs its tail into the body. The tail essentially serves as energy for completing all of the morphological changes occurring during this time. Since the tail is generally long, it takes a little while for the froglet to resorb it, and the transforming froglet can make a choice, to a certain degree, about when to crawl out of the water.

As soon as the tadpole develops arms, its ability to swim is greatly hampered. Thus, staying in the water is a dangerous proposition. However, having a long tail on land is also tricky because the new little froglet will be less able to jump and avoid predators. Thus, we may predict that if the water is safe, the froglet should stay put as long as possible and complete as many metamorphoses as it can before entering the scary new terrestrial world.

On the flip side, if there’s imminent danger in the water, the froglet would probably want to get out and take its chances on land. Let’s see how the different predator treatments and hatching age may have affected the size of the tail when we collected the froglets the morning after they crawled out of the water. Longer tails would imply that they left the water earlier in the window of metamorphosis, whereas shorter tails would indicate that they stayed put longer.

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