Factorial Design

Factorial designs are a form of true experiment, where multiple factors (the researcher-controlled independent variables) are manipulated or allowed to vary, and they provide researchers two main advantages. First, they allow researchers to examine the main effects of two or more individual independent variables simultaneously. Second, they allow researchers to detect interactions among variables. An interaction is when the effects of one variable vary according to [Page 262]the levels of another variable. Such interactions can only be detected when the variables are examined in combination.

When using a factorial design, the independent variable is referred to as a factor and the different values of a factor are referred to as levels. For example, a researcher might examine the effect of the factor, medication dosage, of different ...