The document discusses experimental design and methodology. It describes three types of experimental orientations: descriptive observation, relational correlation, and experimental manipulation and control. It then discusses the importance of establishing causality through meeting conditions like temporal precedence and ruling out rival explanations. Various experimental designs are presented, including between-subjects, within-subjects, and mixed designs. Issues like counterbalancing, sample sizes, and threats to internal and external validity are also covered. Examples of research questions that could be investigated with different designs are provided.

1. Think of three experiments inspired by the classic Eames chair DESIGN 1: EXPERIMENTS purpose problems proof

2. Descriptive orientation Observation - Naturalistic - Field - no controlRelational Orientation Correlational, association - non-intervention - statistical controlExperimental Orientation Control and manipulation DESIGNS

3. Descriptive orientation Observation - Naturalistic - Field - no controlRelational Orientation Correlational, association - non-intervention - statistical controlExperimental Orientation Control and manipulation DESIGNS

4. WHY?

5. MANIPULATION & CONTROL

6. WHY?

7. MANIPULATION & CONTROL CAUSALITY

8. Must be evidence of Mutual relationship (covariation) Temporal precedence (one before the other) Rival explanations ruled out (internal validity) We have to settle for best available evidence David Hume (1711 – 1776) Scottish Philosopher conditions of causality

9. Think of all the things that caused you to be in this room now?

10. Method of agreement (if X, then Y) Method of difference (if not X, then not Y) John Stuart Mills (1806 –1873) English Philosopher Logic of experiments

11. Method of agreement (if X, then Y) Experimental Group Method of difference (if not X, then not Y) Control Group John Stuart Mills (1806 –1873) English Philosopher Logic of experiments

12. http://www.random.org/

13. RANDOM selection allocation

14. How would you know if exercise reduced depression?

15. Designs

16. BETW EEN

17. BETW EEN WITHIN

19. Does therapy reduce depression?

20. Does playing violent games lead to violent behaviour?

21. Is procrastination worse for males or females?

22. Does the university you attend affect your life chances?

23. Are richer people happier?

24. Does gardening improve concentration?

25. Does this lecture influence mood?

26. Does listening to music improve attention?Within or Between?

28. 3x3 BETWEEN BE TW EEN BE TW EEN FACTORIAL

29. 3x3 mixed BE TW EEN WI TH IN MIXED FACTORIAL

30. 2x3 BETWEEN BET WEEN BE TW EEN FACTORIAL

31. 2x2x2 BETWEEN BET WEEN BET WEEN BET WEEN FACTORIAL

32. 3x3 WITHIN WI TH IN WI TH IN FACTORIAL

33. 2x3 WITHIN WIT HIN WI TH IN FACTORIAL

34. 2x2 WITHIN WIT HIN WIT HIN FACTORIAL

35. 2x2 MIXED BET WEEN WIT HIN MIXED FACTORIAL

36. 2x3 MIXED BET WEEN WI TH IN MIXED FACTORIAL

37. And so on....

38. But... How many participants? Counterbalance within designs Statistical procedures....shhh later

39. Does therapy work – if so which works best? How would this be written up? A 2 (time: pre vs post) x 4 (treatment: CBT, Psychotherapy, Exercise, Control) mixed factorial design, with repeated measures on the time variable. What effects? Effect of Time Effect of Condition Interaction of Time and Condition

40. counterbalancing

41. “Help, my experiments got problems...”

42. Threats Internal Validity Can we be sure that the effect is due to the variables we thought? History = If study over time, what else has happened in the mean time? Maturation = If study over time, what has happened to the participants? Instrumentation = Are the instruments valid? Selection = Has this had an effect? Attrition = Have people dropped out? Some more than others?

43. Threats External Validity Can we extrapolate from the study itself? Task = is it ecologically valid? Setting = are the findings limited to a setting? Time = when was the study conducted, could this matter? Participants = can we generalise from them?

44. The psychology of the experiment What the @*!#?

45. ERRORS SYSTEMATIC RANDOM Artifacts

46. ERRORS SYSTEMATIC RANDOM

47. “Did I do ok?” “Did I ruin the study?” “Did I do it right?”

48. Demand Characteristics “Did I do ok?” “Did I ruin the study?” “Did I do it right?” “How should I behave here?” “Did I perform well in my rôle as an experimental subject” Volunteering is a commitment to comply! Don’t ask WHY, just ask WHERE?

49. ERRORS SYSTEMATIC RANDOM Good subjects Evaluation apprehension – look good Experimenter effects Artifacts

51. few or no instructions

52. considerable choice of behaviour

53. lasts for a long timeWhen do situations matter? Like experiments Less like experiments Buss, A.(1989) Personality As Traits. American Psychologist, 44, 1378-1388

54. Let’s have a look at doing some analysis

55. Does therapy work – if so which works best? How would this be written up? A 2 (time: pre vs post) x 4 (treatment: CBT, Psychotherapy, Exercise, Control) mixed factorial design, with repeated measures on the time variable. What effects? Effect of Time Effect of Condition Interaction of Time and Condition