ABSTRACT
Using two or more independent variables This chapter introduces analysis of designs where more than one independent variable is manipulated or where more than one non-experimental factor is observed. In these designs independent variables are known as FACTORS and they each have several levels. As we know, the manipulation of a single independent variable with all other variables held constant is a design that has been criticised for its extreme separation from reality. In normal life, we are affected by several influences together at any one time. The two factor design moves that one step closer to reality by testing the effects of two independent variables (‘factors’) on a dependent variable simultaneously.
The appropriate statistical analysis is termed a two-way ANOVA; three-way ANOVA is for three factors and so on. The analysis of unrelated designs, where all factors use independent samples, is commonly known as a BETWEEN GROUPS ANOVA. Where factors are related (repeated measures or matched pairs) the analysis is a WITHIN GROUPS ANOVA. Where both unrelated and related factors are involved the analysis is a MIXED DESIGN ANOVA.
