Factorial Designs: A Visual Approach

1. Factorial Designs: A Visual Approach No numbers! Research design explained

2. This tutorial is based on the example study described on page 420 of Research designed explained.

3. This tutorial is based on the example study described on page 420 of Research designed explained. • In that study, all participants read 60 statements aloud. These statements were presented as a Powerpoint slide show.

4. This tutorial is based on the example study described on page 420 of your text. • In that study, all participants read 60 statements aloud. These statements were presented as a Powerpoint slide show. • However, not all slide shows were the same.

5. This tutorial is based on the example study described on page 420. • In that study, all participants read 60 statements aloud. These statements were presented as a Powerpoint slide show. • However, not all slide shows were the same. • Some slide shows presented negative statements (e.g., “I feel a little low today”), whereas other slide shows presented positive statements (e.g., “I feel pretty good today”). Thus, some participants read positive statements, whereas others read negative statements.

6. This tutorial is based on the example study described on page 420. • In that study, all participants read 60 statements aloud. These statements were presented as a Powerpoint slide show. • However, not all participants read the same 60 statements. Some read positive statements (e.g., “I feel pretty good today, though”), whereas others read negative statements (e.g., “However, I feel a little low today”). • In addition, the slide shows varied in how fast they presented the statements. Some slide shows presented the statements at a fast rate; others presented the statements at a slow rate. Thus, some participants had to read and say the statements at a fast pace; the other participants did so at a slow pace.

7. Visually, we can diagram the design as follows: Participants Negative statements Positive statements Slow Fast Fast Slow

8. In short, participants saw one of four slide shows: • Slow paced, negative statements show • Fast paced, negative statements show • Slow paced, positive statements show • Fastpaced, positive statements show

9. Thus, the experimenters varied two things: • Pace of the slide show (slow or fast) and • Type of statement (negative or positive)

10. For the purpose of this tutorial, imagine that participants rated their mood on the following scale. UnhappyHappy

11. Thus, a darker color represents a darker mood, and a lighter color represents a lighter mood. UnhappyHappy Interactions

12. As you can see from the next slide, this scale allows us to average participants responses without using numbers. UnhappyHappy

13. Average of Colors 1 & 2 Color 1 Color 2 (Black) (Black) (Black) (Gray) (Gray) (Gray) (White) (White) (White) (Black) (White) (Gray)

14. Now, let’s look at some possible results.

15. Now, let’s look at some possible results. • Let’s start with the manipulations having no effect.

16. Suppose we observed no effect for any of the slide shows: Regardless of condition, everyone ended up in a good (light) mood.

17. Because type of statement does not matter, we could combine the results from the negative and positive statements, like this:

18. Alternatively, because presentation speed does not matter, we could combine (collapse) the results from the slow and fast statements, like this:

19. Finally, because neither presentation speed nor statement type matter, we could combine (collapse) the results into one box, like this:

20. Suppose we observed no effect for any of the slide shows: Regardless of condition, everyone ended up in a bad (dark) mood.

21. Because type of statement does not matter, we could combine (collapse) the results from the negative and positive statements, like this:

22. Alternatively, because presentation speed does not matter, we could collapse the results from the slow and fast statements, like this:

23. Finally, because neither presentation speed nor statement type matter, we could combine (collapse) the results into one box, like this:

24. Suppose we observed no effect for any of the slide shows: Regardless of condition, everyone ended up in a neutral (gray) mood.

25. Because type of statement does not matter, we could collapse the results from the negative and positive statements, like this:

26. Alternatively, because presentation speed does not matter, we could collapse the results from the slow and fast statements, like this:

27. Finally, because neither presentation speed nor statement type matter, we could combine (collapse) the results into one box, like this:

28. In the next 4 slides, let’s look at the case in which positive statements help mood more than negative statements. • This would be called a “statement main effect.”

29. Suppose the only effect was that positive statements had a more positive effect on mood than negative statements. (Slide 1 of 4) Slow and Fast Presentations

30. Suppose positive statements have a more positive effect on mood than negative statements (Slide 2 of 4)

31. Suppose positive statements have a more positive effect on mood than negative statements (Slide 3 of 4) Negative Positive On average, participants getting negative statements are in a darker mood than those getting positive statements, suggesting an effect for statement type.

32. Suppose positive statements have a more positive effect on mood than negative statements(Slide 4 of 4) Negative Positive On average, participants getting the slow slide show are in the same mood than as getting the fast show, suggesting no effect for speed of presentation. Fast Slow

33. In the next 4 slides, let’s look at the case in which fast presentation of statements boosts mood more than slow presentation of statements. • This would be called a “presentation speed main effect.”

34. Statements presented quickly seem to boost mood more than statements presented slowly (Slide 1 of 4) Speed has the same effect for both positive and negative statements Positive Statements Negative Statements

35. Statements presented quickly seem to boost mood more than statements presented slowly (Slide 2 of 4)

36. Statements presented quickly seem to boost mood more than statements presented slowly (Slide 3 of 4) On average, participants getting the slow slide show are in the darker mood than those getting the fast show, suggesting an effect for speed of presentation. Slow Fast

37. Statements presented quickly seem to boost mood more than statements presented slowly (Slide 4 of 4) Negative Same Positive Slow Fast Different

38. Now, let’s look at some interactions. In an interaction, a treatment’s effect in one condition is different from its effect in another condition.

39. Sometimes, interactions occur because a treatment has one effect in one condition, but the opposite effect in another condition. For example, some medications can have positive effects under certain circumstances, but negative effects under others.

40. Interaction: Moodlightens(+) Mood darkens (-) Speeding up the pace improves mood in the negative statements condition, butworsens mood in the positive statements condition.

41. Interaction: Mood darkens (-) Moodlightens(+) Speeding up the pace worsens mood in the negative statements condition, butimproves mood in the positive statements condition.

42. Sometimes, interactions occur because a treatment has an effect in one condition, but no effect in another condition.

43. Interaction: Mood does not change (0) Moodlightens(+) Speeding up the pace has no effect on mood in the negative statements condition, butimproves mood in the positive statements condition.

44. Interaction: Moodlightens(+) Mood does not change (0) Speeding up the pace has no effect on mood in the negative statements condition, butimproves mood in the positive statements condition.

45. Interaction: Mood darkens (-) Mood does not change (0) Speeding up the pace has darkens mood in the negative statements condition, buthas no effect on mood in the positive statements condition.

46. Interaction: Mood darkens (-) Mood does not change (0) Speeding up the pace has darkens mood in the negative statements condition, buthas no effect on mood in the positive statements condition.

47. Sometimes, interactions occur because a treatment has more of an effect in one condition than in another.

48. Interaction: Mood lightens slightly (+) Mood lightens greatly (++) Speeding up the pace has lightens mood slightly in the negative statements condition, butlightens mood considerably in the positive statements condition.

49. Interaction: Mood darkens greatly (--) Mood darkens slightly (-) Speeding up the pace has darkens mood greatly in the negative statements condition, butdarkens mood slightly in the positive statements condition.

50. END