A Computer Program that Demonstrates the Difference between Main Effects and Interactions

Abstract

This article describes a QuickBASIC program for demonstrating the difference between main effects and interactions in factorial designs. The program guides the student through the construction of data patterns corresponding to different combinations of the main effects and the interaction in a 2 times 2 design. Program feedback provides tailored guidance to help students produce the requested patterns of means. The program also generates ideal solutions for comparison. To simulate actual experience, the program generates a data set (N = 80) for each constructed pattern of means and calculates the tests of significance for the main effects and interaction. The program can be used in conjunction with a traditional lecture on factorial designs to improve student understanding of main effects and interactions and to develop student skill in recognizing main effects and interactions from graphical displays.