Planning experiments to detect inadequate regression models

The adequacy of a regression model can be tested by fitting an extended model which reduces to the given model for particular parameter values. The choice of the extended model for nonlinear regression is discussed. Two experimental design criteria are compared and designs are developed for simultaneously providing information about both the original regression model and the hypothesis that the model is adequate. Designs are tabulated for detecting second-order departures from two k-factor models and an example is given of a nonlinear application.