This document discusses quasi-experimental research design, which resembles a true experiment but lacks key components such as random assignment or a control group. Quasi-experiments involve manipulating an independent variable but do not have randomization or a control group. The three most popular quasi-experimental designs are: non-equivalent control group design, time series design, and multiple time series design. Quasi-experiments are used when true experiments are not feasible or ethical.

1. QUASI
EXPERIMENTAL
RESEARCH DESIGN

2. QUASI EXPERIMENTAL DESIGN
OThe prefix “quasi” means, in essence,
“sort of”, or resembling.
OThe word “quasi” means as if or almost,
so a quasi-experiment means almost a
true experiment.
OQuasi-experimental studies take on many
forms, but may best be defined as lacking
key components of a true experiment.

3. QUASI EXPERIMENTAL DESIGN
OA true experiment includes:
(1) randomization;
(2) experimental group and control group; and
(3) Researcher-manipulated variable
OQuasi-experiments involve the manipulation of
an independent variable. However, it lacks
one or both of the essential properties:
randomization and a control group.

4. QUASI EXPERIMENTAL
DESIGN
OIt is used when real experiments are
not feasible and having a control
group would be unethical. E.g.
Giving ill people a placebo
medication.
OIt is used to examine effects that
rely on person factors.

5. ADVANTAGES
O Without extensive pre-screening and
randomization, it reduces the time and
resources needed for experimentation.
O This design is more suitable for real-world
natural setting than true experimental
research designs.
O It reduces the difficulty and ethical concerns
that may surround the pre-selection and
random assignment of test subjects.

6. DISADVANTAGES
O The absence of a control group or lack of
control over the research setting makes the
results of this design less reliable and weak
for the establishment of casual relationship
between independent and dependent
variables.
O Pre-existing factors and other influences are
not taken into account because variables
are less controlled in quasi-experimental
research.

7. Validity in
Quasi-experimental Research
O Internal Validity-refers to the validity of the findings
within the research study.
Problems that can affect internal validity are:
-History -Mortality
-Maturation -Selection Interaction
-Instrumentation -Statistical Regression
-Selection
 For example, Mortality affects the research done if
the number of students tested is not consistent.
Students who leave or move to the school will affect
the data.

8. OExternal validity refers to the extent to
which the results of study can be
generalized or applied to other
members of the larger population being
studied.
For example, if a single class made the
change on 1 elementary school, external
validity questions whether the entire school
or the entire district will be able to make
the change
Validity in
Quasi-experimental
Research

9. Quasi-
Experimental
Designs

10. 3 Most Popular
Quasi-experimental Designs
ONon-equivalent
Control Group
OTime Series Design
OMultiple Time Series
Design

11. Quasi-Experimental Design:
Non Equivalent Control Group
Design
O 2 groups are compared/2 sample groups
O practical when implementing
O practical when analyzing
O can be affected by many extraneous
variables
O popular design among educators

12. Quasi-Experimental Designs
O Non-equivalent control group designs
 Types
1.Non equivalent control group pre-test post-test
design
O1 X O2
O1 - O2
2.Non-equivalent control group post test only design
X O
O
KEY:
X =treatment or intervention
O1 =pre-test
O2 =post-test

13. Quasi-Experimental Design:
Time Series Design
Ouses one sample group
Oinvolves repeated
observations or
measurements over a period
of time both before and after
treatment.
Omeasures significant change

14. Quasi-Experimental Designs
O Time Series Designs
 Types
1. Time Series design
O1 O2 O3 O4 X O5 O6 O7 O8
2. Time Series non-equivalent control group design
O1 O2 O3 O4 X O5 O6 O7 O8
O1 O2 O3 O4 - O5 O6 O7 O8
3. Time Series with intensified treatment (quasi-
experimental)
O1 O2 X O3 O4 X+1 O5 O6 X+2 O7 O8
4. Time series with withdrawn and reinstituted
treatment
O1 O2 X O3 O4 ( -X ) O5 O6 X+2 O7 O8

15. Quasi-Experimental Design:
Multiple Time Series Design
OAdds a control group to
time series design
OAdds credibility to
findings