Experimental research uses manipulation of independent variables and random assignment to test hypotheses about cause-and-effect relationships between variables. Key characteristics include comparing experimental and control groups, where the experimental group receives the treatment and the control group does not. True experimental designs with random assignment are strongest, while quasi-experimental designs lack random assignment. Various designs are used including pretest-posttest and posttest-only with control groups. Factorial designs study interactions between treatments and moderator variables.

1. QUANTITATIVE RESEARCH
METHODOLOGIES
(Experimental Research)

2. EXPERIMENTAL RESEARCH
Best research
methodology to
establish cause-and-
effect relatonships
among variables

3. EXPERIMENTAL RESEARCH
Tests hypotheses
about cause-and-
effect
relationships.

4. EXPERIMENTAL RESEARCH
Dependent VariableIndependent Variable
Experimental or
Treatment Variable
Criterion or Outcome
Variable

5. Essential Characteristics of
Experimental Research
A. Comparison of groups
• 2 groups (experimental & control grps)
• experimental group receives treatment
• control group does not receive treatment

6. Essential Characteristics of
Experimental Research
B. Manipulation of the independent variable
• The independent variable may be
established as one form of the variable
versus another
Example: A study comparing the learning
by doing method with lecture method in
TLE.

7. Essential Characteristics of
Experimental Research
B. Manipulation of the independent variable
• The independent variable may be
established as the presence versus
absence of a particular form
Example: A study comparing the use of
DLP versus no DLP in teaching history.

8. Essential Characteristics of
Experimental Research
B. Manipulation of the independent variable
• The independent variable may be
established as varying degrees of the same
form
Example: A study comparing the effects of
different contact hours on students interest
in Mathematics.

9. Essential Characteristics of
Experimental Research
C. Randomization
• Subjects are randomly assigned to
groups.
• Random assignment:
- individual participants have the
chance of being assigned to any of the
two groups
- eliminates extraneous variables

10. 3 things to remember about randomization
Randomization
1) takes place before the experiment begins
2) is a process of assigning or distributing
individuals to groups not a result of such
distribution
3) forms groups that are equivalent and
differ only by chance

11. GROUP DESIGNS IN
EXPERIMENTAL RESEARCH

12. Weak Experimental Designs
The One-Shot Case Study
A single group is exposed to treatment and
a dependent variable is observed
(measured) to assess the effect of the
treatment

13. Weak Experimental Designs
The One-Shot Case Study Design
X O
Treatment Observation
(Dependent Variable)
Example: suppose you wish to see if a new textbook increasues
student interest in your course (history, science, statistics, etc.)
Weakness: Absence if any control - researcher has no way of knowing
if the results obtained at O are due to treatment X

14. Weak Experimental Designs
The One-Group Pretest-Posttest Design
A single group is measured or observed
before and after the treatment.

15. Weak Experimental Designs
The One-Group Pretest-Posttest Design
O X O
Observation
(Pretest)
Treatment Observation
(Posttest)
Example: suppose you want to assess the effects of weekly
counseling sessions on the attitudes of identified bullies in school
Weakness: Uncontrolled-for threats to internal validity that might
explain the results of the posttest (Example: maturation, data collector
characteristics, etc.)

16. Weak Experimental Designs
The Static-Group Comparison Design
Two existing intact (static) groups are used
Also called nonequivalent control group
design

17. Weak Experimental Designs
The Static-Group Comparison Design
X O
O
Example: Suppose you want to test the effect of a new textbook in increasing
interest of students in class. Find two intact groups, assign the new textbook to
one class and have the other class use the regular textbook, then measure the
degree of interest in both classes at the same time.
Weakness: Uncontrolled-for threats to internal validity (Vulnerable to
maturity and location)
X - treatment
Blank space - control (with no treatment or with a different treatmen)
O - observed
Dash - indicated that the two groups are not randomly assigned

18. Weak Experimental Designs
The Static-Group Pretest-Posttest
Design
Two existing intact (static) groups are used
Pretest is given to both groups
Pretest score is subtracted from posttest
score, permitting analysis of "gain or
change"

19. Weak Experimental Designs
The Static-Group Pretest-Posttest Design
O X O
O O
Weakness: amount of gain often depends on initial performance

20. True Experimental Designs
Subjects are randomly assigned to
treatment and control groups.

21. True Experimental Designs
The Randomized Posttest-Only Control
Group Design
Involves two groups formed by random
assignment
One group receives treatment whike the
other does not, then both groups are
posttested

22. True Experimental Designs
The Randomized Posttest-Only Control Group Design
Treatment
Group
R X O
Control
Group
R C O
R - random assignment of individals to groups
X - treatment/exposure to treatment
C - control group
O - observation (measurement) of the dependent variable

23. Example
The Randomized Posttest-Only Control Group Design
100 randomly selected
teachers
R
50 teachers
X
Dance for
Peace
Training-
Workshop
O
Posttest:
Faculty Self-
Awareness
Questionnaire
R
50 teachers
C
No training
O
Posttest:
Faculty Self-
Awareness
Questionnaire

24. True Experimental Designs
The Randomized Pretest-Posttest
Control Group Design
Involves two groups formed by random
assignment
Both groups are pretested and posttested
Measurements or observations are
collected at the same time for both groups

25. True Experimental Designs
The Randomized Pretest-Posttest Control Group Design
Treatment
Group
R O X O
Control
Group
R O C O
R - random assignment of individals to groups
X - treatment/exposure to treatment
C - control group
O - observation (measurement) of the dependent variable

26. Example
The Randomized Posttest-Only Control Group Design
100 randomly
selected
teachers
R
50 teachers
O
Pretest:
Faculty Self-
Awareness
Questionnaire
X
Dance for
Peace
Training-
Workshop
O
Posttest:
Faculty Self-
Awareness
Questionnaire
R
50 teachers
O
Pretest:
Faculty Self-
Awareness
Questionnaire
C
No training
O
Posttest:
Faculty Self-
Awareness
Questionnaire

27. True Experimental Designs
The Randomized Solomon Four-Group
Design
Involves random assignment of participants to four
groups with two groups being pretested and two
not
One of the pretested groups and one of the
unpretested groups is exposed to treatment.
All four groups are posttested

28. True Experimental Designs
The Randomized Solomon Four-Group Design
Treatment
Group
R O X O
Control
Group
R O C O
Treatment
Group
R X O
Control
Group
R C O
The first two groups represent the pretest-posttest control group
design, while the last two groups represent the posttest-only control
group design.

29. Example
The Solomon Four- Group Design
100
randomly
selected
teachers
R
25
teachers
O
Pretest:
Faculty Self-Awareness
Questionnaire
X
Dance for
Peace Training-
Workshop
O
Posttest:
Faculty Self-Awareness
Questionnaire
R
25
teachers
O
Pretest:
Faculty Self-Awareness
Questionnaire
C
No training
O
Posttest:
Faculty Self-Awareness
Questionnaire
R
25
teachers
X
Dance for
Peace Training-
Workshop
O
Posttest:
Faculty Self-Awareness
Questionnaire
R
25
teachers
C
No training
O
Posttest:
Faculty Self-Awareness
Questionnaire

30. True Experimental Designs
Random Assignment with Matching
Pairs of individuals are matched on certain
variables (choice of variables to match is based
on previous research, theory and/or experience of
researcher)
Members of each matched pair are assigned to
the experimental and control groups at random.

31. True Experimental Designs
The Randomized Posttest-Only Control Group Design,
Using Matched Subjects
Treatment
Group
Mr X O
Control
Group
Mr C O
Mr - Memhers of each matched pair are randomlyassigned to
experimental and control groups

32. True Experimental Designs
The Randomized Pretest-Posttest Control Group Design,
Using Matched Subjects
Treatment
Group
Mr O X O
Control
Group
Mr O C O

33. Quasi-Experimental Designs
No random assignment of
participants or subjects

34. Quasi-Experimental Designs
The Matching-Only Design
Participants (subjects) from intact groups are
matched.

35. Quasi-Experimental Designs
The Matching-Only Posttest-Only Control Group Design
Treatment
Group
M X O
Control
Group
M C O
M - Memhers have been matched but not randomly assigned

36. Quasi-Experimental Designs
The Matching-Only Pretest-Posttest Control Group Design
Treatment
Group
M O X O
Control
Group
M O C O
M - Memhers have been matched but not randomly assigned

37. Quasi-Experimental Designs
Counterbalanced Designs
Each group is exposed to ALL treatments in
different order. Order is determined randomly.
Any number of treatments may be involved.

38. Example
Three-Treatment Counterbalanced Design
Group I X1 O X2 O X3 O
Group II X2 O X3 O X1 O
Group III X3 O X1 O X2 O

39. Quasi-Experimental Designs
Time-Series Designs
Involve repeated observations or measuremetns
over a period of time both before and after
treatment.
01 O2 O3 O4 O5 X O6 O7 O8 O9 O10
Basic Time-Series Design

40. Factorial Designs
with or without random assignment of participants
or subjects
Extend the number of relationships that may be
examined in an experimental study.
The interaction of an independent variable with
one or more moderator variables can be studied.
Moderator variables may be either treatment
variables or subject characteristic variables.

41. Example
Factorial Design (2 x 2 factorial design)
Treatment R O X Y1 O
Control R O C Y1 O
Treatment R O X Y2 O
Control R O C Y2 O
Y1 and Y2 - moderator variables with two levels

42. Example
Factorial Design (2 x 2 factorial design)
X C
Y1
Y2

43. Example
Factorial Design (2 x 2 factorial design)
X
Learning
by Doing
C
Lecture
Y1
(Male)
Y2
(Female)