The four-in-one residual plot displays four different residual plots together in one graph window. This layout can be useful for comparing the plots to determine whether your model meets the assumptions of the analysis. The residual plots in the graph include:

·    Histogram - indicates whether outliers exist in the data

·    Normal probability plot - indicates whether outliers exist in the data

·    Residuals versus fitted values - indicates whether over-dispersion exists, a nonlinear relationship exists, or outliers exist in the data

·    Residuals versus order of the data - indicates whether there are systematic effects in the data due to time or data collection order

For the resin defect data, all seven of the residuals for fits less than 74 are negative. Similarly, all eight of the residuals for fits greater than 96 are negative. This pattern reveals a problem with the model. In this case, the analysts find that interactions that are in the data are not in the model.