This week, the main topic is reexpressing either the x or y variable to straighten a nonlinear pattern that we see in a scatterplot. Although the manipulation may be straightforward, it is possible to miss the main message in this material. Here are some questions that may help in your explanations in the homework.
Question 1: What is a simple description of the pattern in a scatterplot?
Question 2: Why do we prefer to fit lines instead of more complicated curves like quadratic or cubic?
Question 3: Is it possible to straighten all nonlinear patterns by power transformations?
Question 4: Can you think of a situation or an example where it is not possible to straighten by power transformations?
Don't forget to look at your data first -- you may see rightaway that it is not possible to straighten the graph.
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