Chapter 12: Factorial designs: Two independent variables

Factorial Designs

• two or more independent variables (factors)

  • does age affect driving ability

  • does talking on a cell phone affect driving ability

How do researchers study factorial designs

• researchers cross the two independent variables; they study each possible combination of the independent variable

• this is called a 2×2 factorial design; 2 levels of one independent variable are crossed with two levels of another independent variable

  • first IV has 2 levels (cell phone vs no cell phone)

  • second IV has 2 levels (older vs younger)

• the combination of levels of the independent variables define all of the possible conditions of the study

main effects (factorial designs possible outcomes)

• test each independent variable to look for main effects

• overall effects of one independent variable on the dependent variable, averaging other levels of the other independent variable

• simple difference

• two independent variables, there are two main effects

• is there an effect of cell phones use on driving regardless of the age of the driver

main effects (interpreting from a table of means)