Research Methods

1. Research Methods Complex Designs

2. Lecture Outline • One-way Designs • Factorial Designs • Main effects • Interactions

3. One-Way Designs • One-way refers to one independent variable • Two groups design • The simplest one-way design • One IV with 2 levels • Foot-in-the-door technique • Get person to consent to small task first, then ask for larger task • EXAMPLE: Freedman & Fraser (1966) • Went door to door • Small request: Sign petition • Large request: Huge, ugly sign on lawn • Experimental group= small then large • Control group = large request only

4. Foot-in-the-Door Compliance with Large Request

5. More than two levels… • Several reasons you may want more than 2 levels of one IV • A) 2 levels cannot provide much information about the exact relationship between IV and DV • B) 2 levels cannot detect curvilinear relationships • C) May be interested in more than 2 groups

6. 100 90 PERFORMANCE 80 70 60 50 $0 $4 AMOUNT OF REWARD A) Lack of Precise Information • Motivation and performance on a motor task • 2 levels of reward

7. 100 90 PERFORMANCE 80 70 60 50 $0 $1 $2 $3 $4 AMOUNT OF REWARD A) Lack of Precise Information • Increased to five levels • Positive monotonic relationship

8. High DEPENDENT VARIABLE Low Level 1 Level 2 Level 3 B) Curvilinear relationships • Nonmonotonic • Increases in the value of one variable are accompanied by increases and decreases in values of another • Fear and attitude change .

9. C) Interested in More Than Two Things • Effects of animal companionship on nursing home residents • 2 group design: • Dog / No Dog • More than 2 groups • Dog, Bird, Cat, No animal • Stress reducing techniques (Bruning & Frew, 87) • 4 group design • Exercise, management skills training, medication, control • All 3 techniques decreased blood pressure and pulse

10. Number of levels of first IV Number of levels of second IV Number of levels of third IV X X Increasing the IVs: Factorial Designs • Factorial designs • More than one independent variable (or factor) • Determining the number of conditions • 2 x 3 • 6 conditions • 3 x 3 • 9 conditions • 2 x 2 x 2 • 8 conditions

11. A 2 x 2 Design • Head movement and persuasive arguments • Participants listened to a persuasive argument while moving their head • Independent variables • Persuasive argument: Tuition increase or tuition decrease • Head movement: Nod head or shake head • Conditions? • 2 x 2 = 4

12. A 2 x 2 Design Persuasive Argument Movement of Head Tuition decrease Tuition increase Nodding Shaking

13. Main Effects • Effect each variable has by itself • DV: Willingness to accept increases in tuition

14. Main Effect for Head Movement

15. Main Effect for Type of Argument

16. Both Main Effects

17. Interactions • The effect of one independent variable depends on the level of the other • There is an interaction in the persuasive argument study • The effect of the type of argument is different depending on whether the person is nodding or shaking their head • Let’s take a closer look

18. Interactions • We can look at the data to detect the interaction • YUCK!!

19. Interactions • We can look at a line graph 

20. Interactions • Or we can look at a bar graph 

21. Interactions • Ordinal (spreading) interaction • IV1 has an effect under one condition of IV2 but less of an effect under the other condition of IV2. • Disordinal (crossover) interaction • There are no main effects of either IV • The effects of each IV are opposite at different levels of the other IV

22. Ordinal Interaction IV1 has an effect under one condition of IV2 but less of an effect under the other condition of IV2.

23. Another Ordinal Interaction IV1 has an effect under one condition of IV2 but less of an effect under the other condition of IV2.

24. Disordinal Interaction • There are no main effects of the IVs • The effects of each IV are opposite at different levels of the other IV Mood during LEARNING

25. Concept Check • A professor randomly assigns students to one of four conditions: • Learn words in the morning and drink 2 cups of coffee • Learn words in the afternoon and drink 2 cups of coffee • Learn words in the morning and drink no coffee • Learn words in the afternoon and drink no coffee • What are the main effects and the interactions in this design? • What questions would you ask to evaluate these effects?

26. Concept Check • Main effect 1: Coffee factor • Are there any differences in students who received coffee compared to those who didn’t? • Main effect 2: Time of day factor • Are there any differences in students who learned the words in the morning vs afternoon? • Interaction: Does the effect of coffee depend on the time of day? • Coffee might enhance performance in the morning but impair performance in the afternoon.

27. Main Effects & Interactions No main effect of A or B, no interaction Provocations -

28. Main effect of A, no main effect of B and no interaction Provocations -

29. Main effect of B, no main effect of A and no interaction Provocations -

30. Main effect of A and B, no interaction Provocations -

31. No main effect of A or B; interaction Provocations -

32. Main effect of A, no main effect of B; interaction Provocations

33. Main effect of B, no main effect of A; interaction Provocations

34. Main effect of A and B; interaction Provocations -

35. Hands on Activities • Design Identification • Outcomes of Factorial Designs