9.5. Residual Analysis
The graphical method residual analysis allows you to evaluate whether the regression model that has been fitted to the data is an appropriate model and determine whether there are violations of the assumptions of the regression model.
The residual is the difference between the observed and predicted values of the dependent variable for a given value of X.
| Residual = (Observed value of Y) – (Predicted value of Y) (9.13) |
Evaluating the Assumptions
Recall from Section 9.4 that the four assumptions of regression (known by the acronym LINE) are linearity, independence, normality, and equal variance.
Linearity. To evaluate linearity, you plot the residuals on the vertical axis against the corresponding X values of the independent ...
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