Chapter 9 Regression Wisdom

Residuals Residuals are what is left over after the model describes the relationship Must use the residuals to check if the linear model is reasonable

Linear Models Provide a predicted value The farther the new X value is from the Xbar Regression equation is the same as the linear model

Leverage Linear model does not work very well with large residuals A data point can be unusual if its x-value is far from the mean of such x-values. All lines pass through xbar and ybar

Influential If omitting it from the analysis gives a very different model Depends on the leverage and the residual Take a value out and redo the regression

Lurking Variable Not part of a model but affects ways that the models appear We can never be certain of a lurking variable That is way you can never use “causal”.