Handout 12.1:

DESIGNING A FACTORIAL EXPERIMENT

1. What is your dependent variable?

   How will you measure it? Please be specific about what your outcome measure is and how it will be scored.

2. What is your first independent (predictor) variable?
   

   Your independent variable must vary. In your experiment, it will vary from _______________________________________

    (name and briefly describe the first level of your first factor)  to _______________________________________________

    (name and briefly describe the second level of your first factor)

       

   A true independent variable is a treatment that you manipulate. How will you manipulate your first independent variable?

   Is this variable a true independent variable?
   Why or why not?

   Can you make statements about the effects of this variable?
   Why or why not?

3. What is your second independent (predictor) variable?

   This independent variable is a variable because it varies from ________   to ______________.

   Is this variable a true independent variable?
   Why or why not?

   Can you make statements about the effects of this variable?
   Why or why not?

4. Graph your predicted results.

   
   

5. What is your hypothesis about the effect of your first independent variable?
   • Explain how this hypothesis is consistent with your graph. That is, how could someone tell, by looking at your graph, what you are predicting.

   • Why do you think this hypothesis will be supported?

   • Why do you think this hypothesis is worth testing?

6. What is your hypothesis about the effect of your second independent variable?
   • Explain how this hypothesis consistent with your graph.

   • Why do you think this hypothesis will be supported?

   • Why do you think this hypothesis is worth testing?

7. What is your hypothesis about the interaction effect?
   • Explain how your interaction prediction is consistent with the definition of an interaction. Remember that your hypothesis should fit the formula:
     The effect of varying independent variable (A) _______
     on the dependent variable __________
     will be different (circle one: stronger, weaker, opposite) for the
     _____ (insert name for the first level of your "B" [2nd] independent variable in blank)  groups than for the (insert name for B2) ______ groups.

   • Explain how this hypothesis is consistent with your graph.

   • Why do you think this hypothesis will be supported?

   • Why do you think this hypothesis is worth testing?

8. How will you assign participants to condition? Why?

9. How many participants would you use? Why?

10. Fill in the following ANOVA table for your proposed study:

    Source of Variance	Degrees of Freedom
    A (                       )
    B (                       )
    A X B Interaction
    Error
    Total

     

11. Earlier (in number 4), you graphed your predicted results. Below, graph one other possible outcome of your study.

Handout 12.2

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