Package for the Social Sciences

When investigating the impact of predictor variables on an outcome variable or measuring the effectiveness of an educational program, educational researchers and program evaluators cannot ignore the possible influences of interaction effects. The purpose of this paper is to present a procedure that educational researchers can follow in order to increase their understanding of the nature of the interaction effect between a treatment variable and a continuous independent variable. This technique involves the use of three separate analytical techniques implemented in three steps. First, the interaction effect is statistically tested using a multiple regression model. Second, the interaction effect is plotted, and if the interaction effect is disordinal, the intersection point of the regression lines is calculated. Third, the Johnson-Neyman confidence limits are calculated. A list of the computer commands that can be used in conjunction with the Statistical Package for the Social Sciences (SPSS) PC+ compute