Multi-Factor Experiments

Factorial Designs

  • Assess the effect of more than one independent variable on a dependent variable

    • Independent variables also called factors

  • Look at how multiple factors combine to influence the dependent variable

    • One or the other have an effect?

    • An interaction between the 2 factors?

Mixed Factorial Design

  • Some factors are between-subjects variables and some are within-subjects variables

  • Partial/Incomplete Counterbalance

    • One group: difficult/easy AB

    • Other group: easy/difficult BA

Two-Way Factorial Designs (2×2)

  • Two factors (IVs) are manipulated in same experiment

  • Factorial designs are described by the number of independent variables and the number of levels of each variable

Outcomes of Factorial Designs

  • Main effect: indicates that one and only one factor affects the DV or that each factor has an independent effect on the DV

    • Frustration: more aggressive after both types of cartoons when frustrated

    • Cartoon: more aggressive after violent cartoons regardless of how frustrated they are

  • Interaction effect: the relationship between a factor and the DV depends on the level of another factor

    • Children are more aggressive after watching violent cartoons, but only when they are more frustrated