3.6 Assessing the Accuracy of the Model

• RSE can be considered a measure of the lack of fit of the model. a
• $R^2$ statistic provides an alternative that is in the form of a proportion of the variance explained, ranges from 0 to 1, a good value depends on teh application.

$$R^2 = 1 - \frac{RSS}{TSS}$$ where TSS is the total sum of squarse: $$TSS = \Sigma (y_i - \bar{y})^2$$