5.4.C—Describe the form of association of bivariate data using residual plots

Describe the form of association of bivariate data using residual plots.

• A residual plot is a scatterplot of the residuals versus the predicted response values (or the explanatory variable values).
• Residual plots can be used to investigate the appropriateness of the linear regression model for the observed data.
• The linear regression model should only be fit to the data if the data exhibit a linear trend. Apparent randomness in a residual plot for a linear regression model is confirmation of a linear form in the association between the two variables and indicates that the simple linear regression model is an appropriate model for the data.
• Curvature in the residual plot for a linear regression model suggests that the linear model is not the most appropriate model for the data.