ABSTRACT
This article describes a computerized Stroop experiment used to demonstrate the concept of interaction in a factorial experiment conducted by students in my research methods course. The course is a lower division, one-semester introduction to psychological research methods and experimental design with a required 3-hr laboratory. During the first 6 weeks of the laboratory, students run three predesigned experiments of increasing complexity. The first experiment is a simple bilevel design, the second is a multilevel design, and the third is a factorial design. The purpose of this last exercise is to give students some feel for the interaction when they are interpreting the results from a factorial experiment. I designed a computerized experiment that consistently produces an interaction that is interesting and fairly easy to explain. I briefly describe the experiment, the computer program that generates the stimuli, and the results gathered in six classes during the last 3 years.
