Programs for Problems Created by Continuous Variable Distributions in Moderated Multiple Regression

Abstract

It is difficult to detect interactions between continuous variables in field research using moderated multiple regression (MMR). One reason is that multivariate normality, which occurs in field research but not experimental research, suppresses the residual variance of interaction terms. SPSS, SAS, and Matlab programs that expose the extent of this problem for any given data set are provided. Ironically, when significant interactions are found in field research using MMR, this is because the assumption of multivariate normality has been violated, thus rendering the significance tests potentially invalid. The programs presented in this article compute more trustworthy significance levels via data randomization.