Diagnostics

Residuals = observed – model predicted data. They represent the noise left over after the systematic model effects are removed. Use the Diagnostics Tool to display these residuals in simple plots to check your model assumptions

If the residuals lie roughly on a straight line, then the noise is approximately Normally distributed

If the residuals are equally spread out across the plot – the prediction range – & around zero then the noise is constant & centred around zero (no noise). The tram lines help identify outliers or large residual values

If there is a trend in the residuals vs. run order, this would indicate something not in the model was changing over time. E.g., a downward trend may indicate degrading starting material

If the residuals are not normally and consistently spread (e.g. fan out/worsen as the predictions get bigger) use Box-Cox plot to help you choose a transform to try out (i.e. go back to Transform)