4.1 INTRODUCTION4.2 THE STANDARD REGRESSION ASSUMPTIONS4.3 VARIOUS TYPES OF RESIDUALS4.4 GRAPHICAL METHODS4.5 GRAPHS BEFORE FITTING A MODEL4.6 GRAPHS AFTER FITTING A MODEL4.7 CHECKING LINEARITY AND NORMALITY ASSUMPTIONS4.8 LEVERAGE, INFLUENCE, AND OUTLIERS4.9 MEASURES OF INFLUENCE4.10 THE POTENTIAL-RESIDUAL PLOT4.11 WHAT TO DO WITH THE OUTLIERS?4.12 ROLE OF VARIABLES IN A REGRESSION EQUATION4.13 EFFECTS OF AN ADDITIONAL PREDICTOR4.14 ROBUST REGRESSION