let share

1. Experimental
Research Designs

2. Experimental Design
 Advantages
 Best establishes cause-and-effect
relationships
 Disadvantages
 Artificiality of experiments
 Feasibility
 Unethical

3. Causality
 Temporal precedence
 Covariation between IV and DV
 Eliminate alternative explanations

4. Types of Experimental Designs
 Simple True Experimental
 Complex True Experimental
 Quasi-Experimental

5. Types of Experimental Designs
 Simple True Experimental
 Complex True Experimental
 Quasi-Experimental

6. Simple True Experimental
 Characteristics
 Types
 Variations

7. Characteristics of True Designs
 Manipulation (treatment)
 Randomization
 Control group
Characteristics of simple true designs
 One IV with 2 levels (T, C)
 One DV

8. Types
 Randomized posttest control group design
 Randomized pretest-posttest control
group design

9. Randomized posttest control group design
R T Post
R C Post

10. Randomized pretest-posttest control group
design
R Pre T Post
R Pre C Post

11. Advantages & Disadvantages
 Advantages of pretest design
 Equivalency of groups
 Can measure extent of change
 Determine inclusion
 Assess reasons for and effects of mortality
 Disadvantages of pretest design
 Time-consuming
 Sensitization to pre-test

12. Solomon four-group design
R Pre T Post
R Pre C Post
R T Post
R C Post

13. Variations
 Independent groups (between groups)
 Repeated measures (within groups)

14. Repeated Measures Design
 Advantages:
 Fewer subjects needed (less costly)
 Sensitive to finding statistical differences
 Disadvantages:
 Order effect (practice, fatigue, carry-over)

15. Dealing with Order Effects
 Counterbalancing
 n!
 Latin squares

16. Latin Squares
1 2 3 4
A B D C
Row 1
(60) (0) (120) (180)
B C A D
Row 2
(0) (180) (60) (120)
C D B A
Row 3
(180) (120) (0) (60)
D A C B
Row 4
(120) (60) (180) (0)

17. Dealing with Order Effects
 Counterbalancing
 n!
 Latin
squares
 Randomized blocks
 Time interval between treatments

18. Variations
 Independent groups (between) vs.
repeated measures (within) designs
Consider external validity when
deciding which design to use.

19. Types of Experimental Designs
 Simple True Experimental
 Complex True Experimental
 Quasi-Experimental
 Pre-Experimental

20. Characteristics of True Designs
 Manipulation (treatment)
 Randomization
 Control group
Characteristics of simple true designs
 One IV with 2 levels (T, C)
 One DV

21. Complex True Experimental
 Randomized matched control group
design
 Increased levels of IV
 Factorial design
 Multiple DVs

22. Complex True Experimental
 Randomized matched control group
design
 Increased levels of IV
 Factorial design
 Multiple DVs

23. Randomized matched control group
design
M R T Post
M R C Post
• Used in small samples
∀ ↑ cost in time & money

24. Complex True Experimental
 Randomized matched control group
design
 Increased levels of IV
 Factorial design
 Multiple DVs

25. Increased Levels of IV
 Provides more complete information about
the relationship between the IV & DV
 Detects curvilinear relationships
 Examines effects of multiple treatments

26. Reward Amount
$0 $1 $2 $3
DV
Performance level (% complete)
Amount of reward promised ($) IV

27. Increased Levels of IV
DV
Performance level (% complete)
Amount of reward promised ($) IV

28. Complex True Experimental
 Randomized matched control group
design
 Increased levels of IV
 Factorial design
 Multiple DVs

29. Factorial Design
 >1 IV (factor)
 Simultaneously determine effects of 2 or
more factors on the DV (real world)
 Between Factor vs. Within Factor
 ID’d by # of factors and levels of factors
2X2

30. Do differing exercise regimens (hi,
med, lo intensity) have the same effect
on men as they do on women?
 3 X 2 (Exercise Regimen X Gender)
2 factors
 Exercise Regimen – 3 levels
 Gender – 2 levels
 Between factors
 DV?
 Experimental IVs or Participant IVs?

31. Gender
Male Female
High
Exercise
Intensity
Medium
Low

32. Do strength gains occur at the same rate in men
as they do in women over a 6 mo. training period?
Measurements are taken at 0, 2, 4, 6 mo.
 2 X 4 (Gender X Time)
? factors
 Time – 4 levels
 Gender – 2 levels
 Between or within factors?
 DV?
 Experimental IVs or Participant IVs?

33. Time
0 mo. 2 mo. 4 mo. 6 mo.
Gender
Male
Female

34. Cell means, Margin means
Main Effects, Interactions
Time
0 mo. 2 mo. 4 mo. 6 mo.
Gender
Male 50 70 90 130 85
Female 30 60 75 90 64
40 65 83 110 74
Cell means
Margin means Grand mean

35. Time
0 mo. 2 mo. 4 mo. 6 mo.
Gender
Male 50 70 90 130 85
Female 30 60 75 90 64
40 65 83 110 74

36. Parallel lines indicate no Is there
a main
interaction. effect?
Interaction of Exercise Intensity and Gender
70
65
VO2 Max (ml/kg/min)
60
55 Male
50 Female
45
40
35
High Medium Low
Exercise Intensity

37. Is there
a main
Interaction of Exercise Intensity and Gender effect?
70
65
VO2 Max (ml/kg/min)
60
55 High
Medium
50
Low
45
40
35
Male Female
Gender

38. Non-parallel lines indicate an there
Is
interaction. a main
Interaction of Gender and Time
effect?
140
120
Weight Lifted (lbs.)
100
80 Male
60 Female
40
20
0
0 mo. 2 mo. 4 mo. 6 mo.
Time

39. Is there
a main
Interaction Between Gender and Time effect?
140
120
Weight Lifted (lbs.)
100
0 mo.
80 2 mo.
60 4 mo.
6 mo.
40
20
0
Male Female
Gender

40. Interpretation
 Always interpret the interaction first
(graphical)
 If no significant interaction, interpret main
effects

41.  Advantages of factorial designs:
 Greater protection against Type I error
 More efficient
 Can examine the interaction
 Disadvantages:
↑ subject # for between factor designs
Consider external validity when
deciding which design to use.

42. IV A: Exposure to Violence – violent vs.
nonviolent video
IV B: Gender – male vs. female
B1
DV: # ads recalled (0-8)
B2
9
B
1 2
1 1 5 3
A 5
2 9 5 7
5 5 1
1 2
A

43. IV A: Exposure to Violence – violent vs.
nonviolent video
IV B: Gender – male vs. female
B1
DV: # ads recalled (0-8)
B2
9
A: Yes
B: No 5
AxB: Yes 1
1 2
A

44. Complex True Experimental
 Randomized matched control group
design
 Increased levels of IV
 Factorial design
 Multiple DVs

45. Do strength gains occur at the same rate in men
as they do in women over a 6 mo. training period?
Measurements are taken at 0, 2, 4, 6 mo.
Time
0 mo. 2 mo. 4 mo. 6 mo.
Gender
Male 50 70 90 130 85
Female 30 60 75 90 64
40 65 83 110 74

46. Types of Experimental Designs
 Simple True Experimental
 Complex True Experimental
 Quasi-Experimental

47. Characteristics of True Designs
 Manipulation (treatment)
 Randomization
 Control group
 Less control
 More real-world
 Program evaluation

48. Randomized posttest control group design
R T Post
R C Post

49. Randomized pretest-posttest control group
design
R Pre T Post
R Pre C Post

50. Quasi-experimental Designs
 One group posttest-only design
 One group pretest-posttest design
 Non-equivalent control group design
 Non-equivalent control group pretest-posttest
design
 Time series
 Single subject designs (Case study)
 Developmental designs

51. Quasi-experimental Designs
 One group posttest-only design
 One group pretest-posttest design
 Non-equivalent control group design
 Non-equivalent control group pretest-posttest
design
 Time series
 Single subject designs (Case study)
 Developmental designs

52. Randomized posttest control group design
R T Post
R C Post

53. One group posttest-only design
(One shot study)
T Post
No control of IV threats
Use?

54. Quasi-experimental Designs
 One shot study
 One group pretest-posttest design
 Non-equivalent control group design
 Non-equivalent control group pretest-posttest
design
 Time series
 Single subject designs (Case study)
 Developmental designs

55. Randomized pretest-posttest control group
design
R Pre T Post
R Pre C Post

56. One group pretest-posttest design
Pre T Post
•History
•Maturation
•Testing Use control group
•Instrument decay
•Regression

57. Quasi-experimental Designs
 One shot study
 One group pretest-posttest design
 Non-equivalent control group design
 Non-equivalent control group pretest-posttest
design
 Time series
 Single subject designs (Case study)
 Developmental designs

58. Randomized posttest control group design
R T Post
R C Post

59. Non-equivalent control group design
(Static group comparison design)
T Post
C Post
•Selection bias

60. Quasi-experimental Designs
 One shot study
 One group pretest-posttest design
 Non-equivalent control group design
 Non-equivalent control group pretest-posttest
design
 Time series
 Single subject designs (Case study)
 Developmental designs

61. Randomized pretest-posttest control group
design
R Pre T Post
R Pre C Post

62. Non-equivalent control group
pretest-posttest design
Pre T Post
Pre C Post
•Can check selection bias

63. Quasi-experimental Designs
 One shot study
 One group pretest-posttest design
 Non-equivalent control group design
 Non-equivalent control group pretest-posttest
design
 Time series
 Single subject designs (Case study)
 Developmental designs

64. Time series
Pre Pre Pre Pre T Post Post Post Post

65. Quasi-experimental Designs
 One shot study
 One group pretest-posttest design
 Non-equivalent control group design
 Non-equivalent control group pretest-posttest
design
 Time series
 Single subject designs (Case study)
 Developmental designs

66. Quasi-experimental Designs
 One shot study
 One group pretest-posttest design
 Non-equivalent control group design
 Non-equivalent control group pretest-posttest
design
 Time series
 Single subject designs (Case study)
 Developmental designs

67. Developmental Research Designs
Longitudinal Cross Sectional
 Powerful (within  Less time consuming
subject)  Cohorts problem
 Time consuming
 Attrition
 Testing effect

68. Choosing a Research Design
 Best addresses the problem
 Ethics
 Cost in time and money
 Validity (internal & external)