This document discusses quasi-experimental research designs, which involve manipulating independent variables to observe their effects on dependent variables but lack random assignment of subjects to groups or a control group. It describes six types of quasi-experimental designs and their characteristics, advantages in being more practical than true experiments, and disadvantages of increased risk of bias versus experiments.

1. Quasi-Experimental
Research Design
Presented by,
Sushmita Shrestha
M.Sc. in Midwifery

2. Quasi experimental research design
• It involves manipulation of independent variable to observe the effect
on dependent variable; but it lacks at least one of the two
characteristics of the true experimental design: randomization or
control group.
• In other words, this design have an element of manipulation but lacks
at least one of the other two properties that characterize true
experiments: randomization or control group.

3. Quasi experimental research design
contd…
• They are generally used to establish the causality (effect of
independent variable on dependent variable) in situations where
researchers are not able to randomly assign the subjects to groups or
for various reasons no control group is available for an experimental
study.

4. Main characteristics
• Manipulation of the independent variables to observe the effects on the
dependent variables.
• Lack of at least one of the two other essential characteristics of the
true experiment, i.e. random assignment of subject or a control group.
• Quasi-independent variables are used instead of true independent
variables where independent variable does not manipulate in complete
controller situations.

5. Types
1. Non Randomized Control Group Design
2. Non-Equivalent Control Group Post-Test-Only Design
3. Time Series Non-Equivalent Control Group Design
4. Time Series Design
5. Time Series Design with Withdrawn and Reinstitution Treatment
Design
6. One-Group Pre-test-Post-test Design

6. 1. Non randomized control group design
• In this design, experimental and control group are selected without
randomization and dependent variables are observed in experimental
as well as control groups before the intervention.
• Later, the experimental group receives treatment and after that post-
test observation of dependent variable is carried out for both the
groups to assess the effect of treatment on experimental group.
• It is similar to the pretest-post-test control design, except that there is
no random assignment of subjects in experimental and control groups.

7. For eg. A study to assess the effectiveness of TOT training among
teachers of private nursing colleges of Bhaktapur.

8. 2. Non-Equivalent Control Group Post-Test-
Only Design
• This design involves two non-randomized groups, that is experimental
and control, but neither of which is pre-tested before the
implementation of treatment on the experimental group.
• In addition, while treatment is implemented only on the experimental
group, post-test observation is carried out on both the groups to assess
the effect of manipulation.

9. Non-Equivalent Control Group Post-Test-Only
Design contd…
• This design can be helpful in situations where it is not possible to pre-
test the subjects.
• For example, to study the effect of an educational intervention related
to self-care abilities among diabetic patients residing in rural areas,
where randomization was not possible, so diabetic patients of one
village were used as an experimental group and for comparison
diabetic patients of another village were used as a control group.

10. 3. Time Series Non-Equivalent Control Group
Design
• In time series non-equivalent control group design, an investigator
makes series of observations in an experimental and a control group
before implementation of intervention in the experimental group and
again series of observation of outcome variable is made in both
experimental and control groups.
• For example, a study is carried out to assess the effect of VAP
prevention bundle on VAP-related morbidity and mortality among
critically ill patients admitted on selected ICUs of a tertiary care
hospital.

11. Time Series Non-Equivalent Control Group
Design contd…
• In this example, an investigator recruits patients of a selected ICU as
an experimental group and patients of another similar ICU in the same
hospital or another hospital are used as a control group.
• Before intervention is implemented in an experimental group, several
monthly VAP-related morbidity and mortality data are collected in
both selected ICUs (experimental and control group) and after
intervention again monthly morbidity and mortality related to VAP are
collected in both the groups for the comparison.

12. Time series design
• It involves only a single experimental group without a control group
for the comparison.
• It is useful when the experimenter wants to measure the effects of a
treatment over a long period of time.
• Experimental group is pretested repeatedly then exposed to treatment
and then post-tested repeatedly.

13. Eg: Measurement of learners performance on weekly
basis then introducing a new teaching technique then
again measuring on weekly basis.
Figure: Schematic diagram of time-series design

14. 5. Time Series Design with Withdrawn and
Reinstitution Treatment Design
• In this design, an investigator would continue to carry out observation
of variables and implement short-term intervention and again carry out
outcome variable observations and then administer new intervention
and then again observe the outcome variables. Then again an
investigator would administer new treatment and observe the outcome
variable to compare the effect of different interventions.
• For example, an investigator carries out a study to assess the
effectiveness of detergent versus phenolic disinfectants versus
glutaraldehyde disinfectant in reducing flora count for surgical ICU
floor moping at tertiary care hospital.

15. Time Series Design with Withdrawn and
Reinstitution Treatment Design contd…
• In this example, investigator first carries out culture samples during
different shifts and then gets floor moped with detergent and then
again takes culture samples during different shifts and then
implements the floor moping by phenolic disinfectants followed by
culture sample during different shifts and consequently the floor
moping by glutaraldehyde disinfectant, which is followed by the
culture samples to assess the flora count on ICU floor.
• In between two interventions, there could be a wash period to
eliminate the risk of residual effect of previous intervention, which is a
major disadvantage of this design.

16. 6. One Group Pre-test-Post-test design
• A single experimental group is taken, pretest is done. Then, treatment
is administered. And finally post test observation is done to assess the
effectiveness of the treatment.
• Experimental group Pre-test Treatment Post-test

17. One Group Pre-test-Post-test design
contd…
For example: A study to assess the effect of deep breathing on blood
pressure in women with hypertension in selected community of
kathmandu.
Pretest(measure B.P)
Treatment (Deep breathing exercise)
Post-test(measure B.P.)

18. Advantages
• Quasi-experimental designs are more frequently used because they are
more practical and feasible to conduct research studies in nursing,
where in the absence of a large sample size, randomization and/or
availability of control groups are not always possible.
• This design is more suitable for real-world natural setting than true
experimental research designs.

19. Advantages contd…
• It allows researchers to evaluate the impact of quasi-independent
variables under naturally occurring conditions.
• It may be able to establish causal relationship, wherein some of the
hypotheses are practically answered through this design only.

20. Disadvantages
• It is considered as a weak experimental design to establish causal
relationship between independent and dependent variables because it
controls no threat to internal validity.
• Lack of randomization increases the risk selection bias, there is poor
control over confounding variables, which could negatively affect the
study results.

21. Disadvantages contd…
• There is no control over extraneous variables influencing the
dependent variables.
• The absence of a control group or a lack of control over the research
setting makes the results of this design less reliable and weak for the
establishment of causal relationship between independent and
dependent variables.

22. References
• Sharma K. S. Nursing Research and Statistics. 3rd edition. RELX India
Private Limited. Page no: 162-164.
• https://www.slideshare.net/maheswarijaikumar/quasi-experimental-
design-108088766
• https://www.slideshare.net/asmaatiq14/quasi-experimental-method