Experimental research designs aim to establish causal relationships by manipulating an independent variable and controlling other factors. True experimental designs use random assignment to control groups, with the experimental group receiving treatment and the control group not. Key true experimental designs include pre-test post-test control group design, post-test only control group design, Solomon four group design, factorial design, randomized block design, and crossover/repeated measures design. True experimental designs allow for strong conclusions but can be difficult to implement for human or natural setting studies due to ethical and practical challenges.

1. Quantitative
EXPERIMENTAL RESEARCH DESIGN
Unit 8a
Quantitative
Research Design
Prof.Dr.Chinna Chadayan.N
RN.RM., B.Sc (N)., M.Sc (N)., Ph.D (N).,
Professor,
Enam Nursing College – Savar,
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2. What is Research Design?
• Research design is the framework of research methods and
techniques chosen by a researcher to conduct a study. The
design allows researchers to sharpen the research methods
suitable for the subject matter and set up their studies for
success.
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3. Characteristics of a good design
⚫Control of bias.
⚫Capableof obtaining the mostreliableand valid data.
⚫Helpsan investigator avoid making mistaken
conclusions
⚫Control thevarious threatsof validity, both internal
and external.
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4. ELEMENTS OF RESEARCH DESIGN
SAMPLE &
SAMPLING
SOURCES OF
DATA
COLLECTION
TOOLS AND
METHODS
DATA
ANALYSIS
APPROACH
 Research is a systematic investigation of discovering new knowledge or
contributing to generalized knowledge. It follows a unique structure that is
prescribed in the research design. So, to yield success from research, it is
important to include elements that help solve the problem quickly.
 Here are some of the elements of good research design that incite great
results:
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5. CLASSIFICATION OF RESEARCH DESIGN
True-
Experimental/RCT
1.Pre Test - Post Test
control group Design
2.Post Test Only
control group Design
3.Solomon Four group
Design
4 Factorial Design
5. Crossover Design /
Repeated measures
design
6.Randomized Block
Design
Quasi- Experimental
1. Nonequivalent control
group pretest posttest
Design
2. Nonequivalent control
group posttest only
Design
3. Time series Design
series
control
4. Time
nonequivalent
group design
Pre-
Experimental
1. Single group
Post-test only
Design
2. One group pretest
posttest design
1. Descriptive RD
i. Univariant Desc Design
a) Cross sectional DS
b) Longitudinal DS
ii. Comparative descriptive
design
2. Correlational RD
i. Cohort RD
a) Prospective CD
b) Historical CD
c) Ambispective Cohort
Design
ii. Case control RD
a) Nested case control
Design
iii. Analytical Cross Sec
Design
3. Exploratory RD
4.Surver RD
1.Case Study
2.Ethnography
3.Phenomenology
4.Grounded
theory
5.Participator
y action
Research
1.Triangulation
2.Explanatory
3.Exploratory
4.Embedded
Experimental Design Non- Experimental Design
Quantitative Design Qualitative Design Mixed Methods
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8. Quantitative Research Design
Experimental Design
True- Experimental /
RCT (Randomized Control Trail)
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9. Experimental Design
⚫True experimental research designs are those where researchers have
complete control over the extraneous variables & can predict confidently
that the observed effect on the dependable variable is only due to the
manipulation of the independent variable.
⚫Control over extraneous variables.
⚫Observed effect on dependent variable is only due to the manipulation of
independent variable
⚫A true experimental research design must essentially consist of the
following three characteristics:
1. Manipulation
2. Control
3. Randomization
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10. Quantitative Design
Experimental
True- Experimental/
RCT
Pre Test - Post Test control group Design
1) randomly assign subjects to Experimental or control groups;
2) administer the pre-test to all subjects in both groups;
3) ensure that both groups experience the same conditions except that in
addition the experimental group is given the treatment;
4) administer the post-test to all subjects in both groups;
5) assess the amount of change on the value of the dependent variable from
the pre-test to the post-test for each group separately.
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12. Quantitative Design
Experimental
True- Experimental/
RCT
With this research design, test units are randomly assigned to the
experimental and control groups. No Pre –test.
Only the experimental group is exposed to the treatment.
Then only post –test is measured for both experimental and control
groups.
But, there is only one measurement is taken.
Post Test Only control group Design
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13. Quantitative Design
Experimental
True- Experimental/
RCT
Post Test Only control group Design
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14. Quantitative Design
Experimental
True- Experimental/
RCT
• In a Solomon four group design, the participants in the study are
randomly assigned to four different conditions:
• a) intervention with pre-test and post-test,
• b) pre-test and post-test with no intervention,
• c) intervention with only post-test,
• d) only post-test with no pre-test & intervention.
Solomon Four group Design
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16. Quantitative Design
Experimental
True- Experimental/
RCT
• In factorial design, researcher manipulates two or more independent
variables simultaneously to observe their effects on the dependent
variables.
• This design is useful when there are more than two independent
variables, called factors to be tested.
• For example, a researcher wants to observe the effect of two
different protocols of pain management for cancer patients when
performed at different frequencies in a day.
• This design also facilitates the testing of several hypothesis at a
single time.
• Typical factorial design incorporates 2X2 or 2X3 factorial, but it can
be in any combination.
• The first number (B) refers to the independent variables or the type
of experimental treatments, & the second number (A) refers to the
level or frequency of the treatment.
Factorial Design
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17. Frequency of
Management
Protocols of the pain Mangement
Opioid (B1) NSAID(B2)
Once Daily (A1) A1, B1 (G1) A1, B2 (G4)
Twice Daily (A2) A2, B1 (G2) A2, B2 (G5)
Thrice Daily (A3) A3, B1 (G3) A3, B2 (G6)
Quantitative Design
Experimental
True- Experimental/
RCT
Factorial Design
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18. Quantitative Design
Experimental
True- Experimental/
RCT
Control of inherent differences between experimental
subjects & differences in experimental conditions is one of
the difficult problems faced by researcher in biological
sciences.
When there are a large number of experimental comparison
groups, the randomized block design is used to bring
homogeneity among selected different groups.
This is simple method to reduce the variability among the
treatment groups by a more homogeneous combination of the
subjects through randomized block design.
Randomized Block Design
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19. For example, a researcher wants to examine the effects of
three different antihypertensive drugs on patients with
hypertension.
In this example, to ensure the homogeneity among the
subjects under
• treatment, researcher randomly places the subjects in
homogeneous groups (blocks) like patients with primary
hypertension, diabetic patients with hypertension, & renal
patients with hypertension .
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20. Types of
antihypertensive
drugs
Blocks
Patients with
primary
hypertension (I)
Diabetic patients
with hyper
tension (II)
Renal patients
with
hypertension
(III)
A A, I A, II A, III
B B, I B, II B, III
C C, I C, II C, III
Quantitative Design
Experimental
True- Experimental/
RCT
Randomized Block Design
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21. Quantitative Design
Experimental
True- Experimental/
RCT
 In this design, subjects are exposed to more than one treatment, where subjects are randomly
assigned to different orders of treatment.
 It is also known as ‘repeat measures design’.
 This design is more efficient in establishing the highest possible similarity among subjects
exposed to different conditions, where groups compared obviously have equal distribution of
characteristics.
 Through crossover design is considered as an extremely powerful research design, sometimes it is
not effective because when subjects are exposed to two different conditions, their responses of the
second condition may be influenced by their experience in the first condition.
Crossover Design / Repeated measures design
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22. For example, when we are comparing the effectiveness of the
Opioid drug on group I & NSAID on the subjects of group II.
Later, the treatment is swapped, where group I receives the
NSAID & group II receives Opioid. In such studies, subjects
serve as their own control.
Groups Protocols of the mouth care
Group I Opioid (α1) NSAID (α2)
Group II NSAID (α2) Opioid (α1)
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23. ADVANTAGES OF TRUE EXPERIMENTAL DESIGN
 Experimental research designs are considered the most powerful designs to establish the causal relationship between
independent & dependent variables.
 Where the purpose of research is explanation, causal relationship may be established among the variables by
experimentation, especially in studies involving physical objects, where the variables are more easily controlled than in human
studies.
 In this studies, the controlled environment in which the study is conducted can yield a greater degree of purity in observation.
 Conditions not found in a natural setting can be created in an experimental setting, where the independent variable is
manipulated by investigator.
 In the experimental approach, we can often create conditions in a short period of time that may take years to occur
naturally. For example, in genetic studies we can breed strains in very small time, which would take a long time in nature to
occur.
 When the experiment is conducted in a laboratory, experimental unit, or other specialized research setting, it is removed from
the pressure & problems of real-life situations & the researcher can pursue his or her studies in a more leisurely, careful, &
concentrated way.
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24. DISADVANTAGES OF TRUE EXPERIMENTAL DESIGN
Most of the times, the results of experimental research designs cannot be
replicated in studies conducted on human beings due to ethical problems.
For certain research problems, because of the danger to physical &
psychological health of the human subjects, it is not possible to conduct
experiments on human beings.
Many of the human variables neither have valid measurable criteria nor
instruments to measure them. For example, patient welfare or level of
wellness cannot be measured on any scale or by any instrument. In these
situations, if a refined experimental design is used, there may be a mismatch
of research design & the variable- measuring instruments.
In experimental studies conducted in natural settings like hospitals or
community, it is not possible to impose control over extraneous variables.
Another disadvantage of the experimental research design is that it is very
difficult to get cooperation from the study participants, because it may
involve medical or surgical treatment or intervention, which may make the
prospective subjects reluctant to participate in research study.
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