Main effects: a main effect is the effect that each independent variable by itself has on the dependent variable, essentially, the main effect pretends that the other independent variable didn"t exist in the experiment. Interactions: there is also the possibility that interaction exists, an interaction between independent variables indicates that the effect of one independent variable is different at different levels of the other independent variable. Therefore, the ivxpv design is not fully a true experiment: the simplest ivxpv design includes one manipulated independent variable that has at least two levels and one participant variable with at least two levels. Interactions illuminate moderator variables: a moderator variable in uences the relationship between two other variables, changes the relationship between the other variables, moderator variables may be aspects of the situation, or person variables. Independent groups: in a 2 x 2 factorial design, there are four conditions.