Limitations of dummy coding and nonsense coding as methods of coding categorical variables for use as predictors in multiple regression analysis are discussed. The combination of these approaches often yields estimates and tests of significance that are not intended by researchers for inclusion in their models. (SLD)

The uses and restrictions of commonality analysis are described. Commonality analysis has been increasingly used as a method to examine the relative importance of independent variables, through the partitioning of variance among the variables of the regression equation into unique and common components. The effects of all other independent…

Educational research on the factors of student achievement has been limited by its failure to consider the multilevel or hierarchical nature of most data. This study used a nonexperimental regression-based procedure, hierarchical linear modeling (HLM), to empirically develop a predictive model of fifth-grade achievement in reading and mathematics…