Primer on Multiple Regression Coding: Common Forms and the Additional Case of Repeated Contrasts

Abstract

The use of categorical variable coding has a long history in the application of multiple regression (MR) techniques. The primary purpose of this article is to review and clarify existing MR coding techniques-such as dummy, effect, and contrast coding-and to discuss their properties with reference to analogous procedures in the traditional analysis of variance (ANOVA) model (such as simple, deviation, Helmert, and trend contrasts). Furthermore, in this article, I introduce MR codes equivalent to repeated contrasts in ANOVA. Such explicit ties between MR coding techniques and ANOVA contrasts should increase the availability of both sets of procedures to students of statistics.