STATISTICAL INTERACTION REVISITED Regina

To have valid meaning, "statistical interaction" must be consistent with biological or physical interaction which is defined as mutual (dependent) action of factors contributing to the response effect. In mathematical and statistical response models the parameter representing interaction depends on the model concerned. Factorial experiments, discrete response, and regression models are discussed. The commonly used definition of statistical interaction-as "departure from additivity"-has valid meaning only, where response is represented as a sum of contributions of different factors, and cannot be accepted as the definition of interaction.