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MicroExam 3 - Based on what you know about economics and...

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Micro-Exam 3 ESM 206B Winter 2008 Once you read this file, you may not ask for help from your peers or the instructors, nor may you discuss with them any of the concepts from the first problem set. If you have a question about how to run the software, you may ask your instructors (not your peers). Your solution is due to Heather by 4 PM on Tuesday, Feb. 5. Please email your answers to her or put a hard copy of your answers in her mailbox. Good luck!
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You will continue to analyze the exotic species dataset. 1. (15 points) Construct a model where the dependent variable is Prop_exotic and the independent variables are GDP, M_imports, and the interaction between them (in R, your formula should look like Prop_exotic ~ GDP * M_imports , or alternatively Prop_exotic ~ GDP + M_imports + GDP : M_imports ). Report the parameter estimates and P values. 2. (15 points) Making reference to the variable descriptions on the course website, explain what the interaction term (the product of GDP and M_imports) represents.
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Unformatted text preview: Based on what you know about economics and biological invasion, make an argument for why this quantity should (or should not) be related to a country’s invadedness. 3. (20 points) Would you feel justified in removing any of the independent variables from the model in part 1? Why or why not? 4. (20 points) For simplicity, create a new variable which is the product of GDP and M_imports. Run a model where this is the only independent variable. Is this model better than the model you ran in the previous microexam (using GDP)? Why or why not? 5. (10 points) Examine the variables in the dataset, and identify one or more that you think might influence invadedness (you can construct your own variables that represent sensible combinations of the dataset variables, if you wish). List these variables, and explain why you think each of them might be important. 6. (20 points) Add the new variables to the model from part 4. Is your new model better? Why or why not?...
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