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  3. Causal Inference with R - Regression

Exercise

Toying with OLS I: Outliers

Although the math behind determining an OLS regression model is complicated, understanding what it's trying to do is surprisingly straightforward. Understanding how regression models work can yield important insight into understanding how they can be biased. In this question, we will examine how outliers can effect regression slopes. Using data provided by the popular online auctioneer eGulf about the relationship between WePhone age and sales price, follow the sample code to answer the following question about outliers:

Instructions

100 XP
  • 1) Refresh our memories on what the eGulf data looks like.
  • 2) Run a glm model on how a phone's age affects its sales price on eGulf.
  • 3) Examine a graph of this relationship.
  • 4) Examine the impact of outliers at different phone ages through graphs.
  • 5) Decide when outliers will have the least impact in this regression.