In a three-way analysis of variance, in which significant interaction among the involved factors is detected, it might be important to get the fractioning of the interaction degrees of freedom added to the degrees of freedom of the involved factors. In the case of a significant triple interaction, the effecet of one nested factor is usually checked against the combined effect of the remaining factors. The main aim of this research work has been to get the sum of squares of such effect through the CONTRAST command of PROC GLM, available in the SAS computer program. The feasibility of checking hypothesis and the application of orthogonal contrasts is evaluated through the checking of the obtained results. A numerical example is provided.
three-way layout; interaction; decomposition of interaction
