In a two-way factorial research design, what is being tested?

In a two-way factorial research design, the primary focus is on examining two independent variables (factors) to determine their individual effects on a dependent variable as well as the interaction effect between them. This design allows researchers to test two main effects independently, which assess the impact of each independent variable on the dependent variable, and one interaction effect that explores how the combination of these two variables affects the dependent variable.

The interaction effect is particularly significant because it can reveal that the effect of one independent variable may differ depending on the level of the other independent variable. This complexity in relationships is essential in understanding how these variables interrelate in influencing the outcome being studied. Therefore, the correct answer highlights that a two-way factorial design evaluates both main effects and their interaction, providing a comprehensive analysis of the factors at play.