The document discusses experimental design in quantitative research. It explains that experimental design involves manipulating an independent variable and comparing its effects on a dependent variable between groups, while controlling for extraneous variables. Key aspects of experimental design discussed include having an intervention, making comparisons between groups, using control groups, determining when to collect data, selecting research sites, and communicating with subjects.

1. EXPERIMENTAL DESIGN
Dr.(Mrs.) A.V.Raman
Dean
Omayal Achi College of Nursing
Avadi, Chennai

2. INTRODUCTION TO RESEARCH DESIGNS
Quantitative research design
• Research design of a study spells out the
basic strategies that researchers adopt to
develop evidence that is accurate and
interpretable
• The research design incorporates some of
the most important methodological
decisions that the researchers make
particularly in quantitative studies

3. ASPECTS OF QUANTITATIVE
RESEARCH
• Intervention
• Comparisons
• Control of extraneous variables
• Timing of data collection
• Research sites and settings
• Communication with the subjects

4. INTERVENTION
In some studies nurse researchers want to test the
effect of specific intervention on dependent
variable (for e.g.. the effect of specific
intervention on labor and neonatal outcome)
COMPARISON
The most common types of comparisons are
1. Comparisons between two or more groups (The
hypothesis that the drug tamoxefin reduced the
rate of breast cancer in high risk women could be
tested by comparing women who received
tamoxefin and those who did not)

5. 2.In certain instances it is desirable to make
comparisons for the same study participants
(e.g. studying patients heart rate before and after
intervention,
Comparing low back pain for patients lying in
two different positions)
CONTROLS FOR EXTRANEOUS VARIABLES
The complexity of relationships among human
characteristics often makes it difficult to answer
research questions unless efforts are made to
isolate key research variables and control other
factors extraneous to the research questions

6. TIMING FOR DATA COLLECTION
In most studies data are collected from
subjects at a single point of time (for e.g. the
subjects might be asked on a single
occasion to describe the health promotion
behavior)
In some designs we contact the subjects
in multiple time (e.g. to observe the growth
pattern 3 monthly) Hence the researcher
must decide on the number of data
collection points needed to address the
research question properly

7. RESEARCH SITES AND SETTINGS
sites are the overall location for
research
Settings are the more specific place
where data collection will occur
sites and settings to be selected so as to
maximize the validity and reliability of
th data in designing a study. The setting
should be natural and avoid anxiety
promoting or foreign to the subjects
experiences

8. COMMUNICATION WITH THE SUBJECTS
 Decide how much information to be
given to the participants
 Full disclosure of the study?
 Consent Oral or written?
 Think about the reading and
comprehension level of the subjects
 Who will provide the information?
 What additional questions from the
subjects are expected?
 Debriefing sessions?

9. EXPERIMENTAL DESIGN
Science answers questions with experiments

10. EXPERIMENTAL DESIGN
 An experiment is a scientific
investigation in which
observations are made and data
are collected according to a set
of well defined criteria. In an
experiment, researchers are
active agents not passive
observers.

11. The procedures developed
by physical scientists were
profitably adopted by
biologists during the 19 th
century, resulting in many
achievements in physiology
and medicine.

12. DEFINITION
Experimental method is an
empirical research method used
to examine a hypothesized
causal relationship between
independent and dependent
variables.

13. DEFINE THE PROBLEM
Begin by asking a question about
your topic
What is a good question for an
experiment?
One that is testable with the
materials at hand

14. Now we need a hypothesis to
guide our investigation.
What is a hypothesis?
Your best thinking about how the change
you make might affect another factor.
Tentative or trial solution to the
question. An if ………… then …………
statement.

15. CHARACTERISTICS OF
EXPERIMENTAL DESIGN
A true experimental
design is characterized
by Manipulation,
Control , and
randomization

16. MANIPULATION
Refers to the process by
which the researcher
manages the independent
variable in order to study the
effect on the dependent
variable.

17. EXAMPLE
. Gentle massage is effective as a pain relief
measure for elderly nursing home residents
The Independent variable is gentle massage
which could be manipulated by giving some
patients the massage intervention and
withholding it for others
Then it is possible to compare the pain level
(dependent variable) in the two group to
see if differences in receipt of the
intervention resulted in degree of pain
levels

18. CONTROL
The experiment must be organized
so that the extraneous factors are
prevented from operating and
confusing the outcome which is
to be appraised.

19. Control is acquired by
manipulating by randomizing,
by careful preparation of the
experimental protocols, and
by the use of a comparison
group or groups.

20. EXAMPLE
• If a researcher wanted to supplement diet of
the low birth baby with a particular nutrient
for 2 weeks, the weight gain at the end of 2
weeks would tell us nothing about the
treatment effectiveness
Suppose an average 1 kg. weight gain is
noted does this gain support the conclusion
that nutrition supplement (IV) caused the
weight gain (DV)

21. The answer will be NO? because babies
normally gain weight as they mature
Without a control group- a group that does not
receive the nutritional supplements it is
impossible to separate the effects of
maturation from those treatment
Therefore the term CONTROL GROUP
refers to a group of subjects whose
performance on a dependent variable is used
to evaluate the performance of the
experimental group on the same dependent
variable

22. RANDOMISATION
The term random essentially means that every
subject has an equal chance of being assigned
to any group. Randomization is the process
that first ensures every unit in the target
population has an equal chance of being
chosen for the study sample, and then
ensures that each unit in the study sample
has on equal chance of being assigned to
either the experimental or the control group.

23. EXAMPLE
The effectiveness of a contraceptive health
education programme for multiparous
women. Two groups of subjects were
included .One group was given
intervention and other was not. The
women in the sample are likely to differ
in age, education, and attitude This
would affect the woman's diligence in
practicing contraception

24. Although randomization is a preferred
scientific method for equalizing the
groups, there is no guarantee that the
group will in fact be equal Therefore we
need a procedure to consciously control
of those characteristics of subjects that
are likely to affect the outcome is called
MATCHING (e.g. if matching were used in
contraceptive education, then the
researcher might ensure that if there was
a married 38 year old woman with six
children in exp. Group, then there will also
be 38 year old woman with six children in
control group

25. The antecedent event in a
proposed causal
sequence is called the
“independent variable”.

26. The measured effect in
the causal sequence is
called the
“dependent variable”.

27. Eight classes of extraneous variables
may especially interfere with research
on human subjects, history,
maturation, testing, instrumentation,
statistical regression selection,
mortality and interaction among these.
• History, the specific events occurring
between the first and second
measurement in addition to the
experimental variables

28. 2. Maturation, process within the respondents
operating as a function of the passage of time
per se (not specific to the particular events),
including growing older, growing hungrier,
growing more tired and the like
3. Testing, the effects of taking a test upon the
scores of a second testing
4. Instrumentation, in which changes in the
calibration of a measuring instrument or
changes in the observers or scores used may
produce changes in the obtained
measurements

29. 5. Statistical regression, operating where
groups have been selected on the basis of
their extreme scores
6. Biaser resulting in differential selection of
respondents for the comparison groups ?
7. Experimental mortality, or differential loss
of respondents for the comparison groups
8. Selection-maturation interaction etc.,
which in certain of the multiple group
quasi-experimental designs, might be
mistaken for the effects of the
experimental variable.

30. PRINCIPLE GUIDELINES OF
EXPERIMENTS
The MAX-MIN-CON. By Kerlinger 1986.
The abbreviation stands for the following.
MAX-Maximize experimental variable
MIN- Minimize error variance.
CON-Control extraneous variance.

31. MAJOR STEPS IN
EXPERIMENTAL DESIGN
1. Delineate the population or universe to
be studied (i.e. the set of subjects or
objects that share a common observable
characteristic)
2. Select a sample from the population by
random sampling
3. By random assignment, sub-divide the
sample into two sub-samples

32. 4.. Specify one sub-sample, the
experimental group and other the control
group
5. Before introducing the independent
variable, observe and record all
important characteristics of the two
groups
3. Introduce the independent variable into
the experimental group but withholds it
from the control group
7. After introducing the independent
variable, observe the dependent variable
in both experimental and control group

33. 8. Compare the changes that occur in
the experimental group with those
that may have occurred in the
control group
2. Record the difference
10.Compare these values with
statistically computed values that
judge the significance of the
difference, and indicate whether or
not the observed differences could
have occurred by chance.

34. TYPES OF EXPERIMENTAL
DESIGN
The investigator planning an experiment
has many experimental design option to
choose. Experimental designs fall into
three major categories.
b)True or classical experimental design
c)Quasi-experimental design
d)Pre-experimental design.

35. TRUE OR CLASSICAL EXPERIMENTAL
DESIGN
• TRUE OR CLASSICAL EXPERIMENTAL DESIGN
• True or classical experimental design
includes six major designs. They are
• Pre-test___ post - test control group
design
• Solomon four – group design
• After/ post - test __ only experimental
design
• Factorial design
• Randomized block design
• Cross over design or repeated
measures design.

36. T he most commonly used in nur sing
studies, ar e discussed as nomenclatur e
used and definitions developed by
Campbell and Stanley ( 1963).
 The standard notations that are helpful
in under standing alternative
experimental design are -
 ‘x’ To denote the experimental
manipulation. (Treatment or
intervention)
 ‘O’ To denote observations or
measurement
 ‘R’ To denote randomization

37. • PRE-TEST POST-TEST
CONTROL GROUP DESIGN
Experimental Experimenta Post
Pretest
l Treatment
group test
Random
assignme
nt
Control group Pretest Post test

38. EXAMPLE
Effectiveness of antenatal
nutrition education on
pregnancy and labor outcome
among primi para mothers
attending out patient department
of selected hospitals Madurai
2007-2009

39. 2. Solomon four group design is a
complex particularly useful in studies of
developmental phenomena and permits the
investigator to differentiate many effects.
Experimental Experimental
Pretest Post test
Treatment
group
Random Control group Pretest Post test
assignment
Experimental Experimental Post test
Treatment
group
Control group Post test

40. EXAMPLE
Effectiveness of workshop on
management of HIV to improve
the nurses attitude toward
patients with AIDS admitted in
selected hospitals , Madurai
2006-2008

41. 3. Post- test only control groups design
this design, which is sometimes called after only control
group designs, is composed of two randomly assigned
groups, but neither of which is pre tested or pre
measured in the before period of time.
Post
Experimental Experimental
-test
group treatment
Random
assignment
Control Post
group
-test

42. EXAMPLE
 Effects of holding the newborns on
paternal bonding behavior
 The researcher randomly assigned 36
first time fathers attending
uncomplicated deliveries of normal
infants to experimental and control
group (Those who held and did not
hold their infants at delivery)12-36
hours after the babies were born
bonding behavior frequencies were
recorded and observed the outcome

43. 4. Factorial design
In this design testing of multiple
hypotheses is done in a single experiment
In factorial experiments subjects are assigned
at random a specific combination of
conditions
e.g. Does auditory stimulations have a more
beneficial effect on the development of
premature infants than tactile stimulation?
(effect is weight gain and cardiac
responsiveness)

44. EXAMPLE
Type of stimulation
AUDITORY TACTILE
A1 A2
Daily 15 Min A1 B1 A2 B1
Exposure B1
30 Min. A1 B2 A2 B2
B2
45 Min. A1 B3 A2 B3
B3

45. 1. Randomized Block Design
There are two factors (independent
variables) but one factor is not
experimentally manipulated.
e.g. Compare the effects of tactile
versus auditory stimulation for female
vs male infants.
It can be structured as 2x2 experiment,
with type of stimulation as one factor
and gender as the other factor

46. • Cross over design (or Repeated
measures design)
It involves the exposure of the same
subjects to more than one experimental
treatment
e.g. Effectiveness of two alternative
back rest position ( flat, horizontal vs.
30o elevation) on intracranial and
cerebral perfusion pressures in brain
injured adults

47. PRE-EXPERIMENTAL DESIGNS
• The one –shot case study or
single case study
→ The study design has a total
absence of control, it is
considered to be little value as
an experiment.

48. 2.One-GroupPretest-posttest
design
Only one group is observed before
and after the independent variable
is introduced. Loss of the control
group decreases the usefulness
of the study but may be necessary
in cases where it is not possible
or feasible to have control groups

49. EXAMPLE
Effectiveness of selected
nursing intervention on
knowledge and level of
satisfaction among clients
with stroke

50. ADVANTAGES OF EXPERIMENTAL
DESIGN
1.True experiments are the most powerful
method for testing hypothesis of cause and
effect relationship between variable because of
the rigours, precision and control properties of
experimental design.
2. This ‘if then’ type of relationship is important
to nursing and medical researchers because of
its implications for predication and
explanation.

51. 3.Though the control imposed
by manipulation comparison
and randomization,
alternative explanation to a
cause interpretation can be
ruled out or discredited.

52. DISADVANTAGES OF EXPERIMENTAL
DESIGN
1. Some variables are not feasible or ethical
to manipulate e.g., assessing pregnant
women to take a new drug found to be
dangerous to fetal development would not
be ethically possible.
2. Randomization and otherwise equal
treatment of control and experimental
group can occur in a laboratory, but these
conditions do not resemble what goes
under real world conditions, and
experimental findings can therefore be
based on rather artificial circumstance

53. 3. Experimental design attempt to
reduce variable to measurable
terms. Many of the phenomena
that are important to science in
nursing are complex,
multidimensional and holistic, and
defy the reductionism that has
worked reasonably in the physical
or natural sciences.

54. QUASI EXPERIMENTAL
DESIGN

55. DEFINITION
It is a research design in
which the researcher initiates
an experimental treatment but
some characteristics of a true
experiment is lacking.

56. PURPOSES
 To provide alternative means of
examining causality in situations
not conducive to experimental
group.
 To facilitate the search for
knowledge and examination of
causality in situations in which
complete control is not possible.

57. RANDOM ASSIGNMENT
It is a procedure used to
assign subjects to
treatment or control
groups randomly.

58. COMPARISON GROUPS
Comparison groups are not selected using
random sampling and do not receive the
experimental treatment.
Types of comparisons groups:
Groups that receive no treatment.
Groups that receive placebo treatment
Groups that receive usual treatment.
Groups that receive second experimental
treatment.

59. TYPES OF QUASI EXPERIMENTAL
DESIGN.
QUASI
EXPERIMENTAL
DESIGN
Non equivalent Interrupted
control group times series
design design

60. NON EQUIVALENT
COMPARISON
GROUP DESIGNS

61. 1. ONE GROUP POSTTEST ONLY
DESIGN
It is referred to as pre-experimental rather
than quasi experimental where manipulation of
Independent variable is done and posttest is
conducted to measure the outcome.
Manipulation of Measurement of
Dependent variable Independent variable
Post test
Treatment
Example
Outcome of Antenatal Education on pregnancy and
labor .

62. 2. POSTTEST ONLY DESIGN WITH A
COMPARISON GROUP
In this design a comparison group is introduced
to determine the efficacy of the treatment and after
manipulation of independent variable only posttest
is conducted.
Experimental Group
Treatment
Post test
Non equivalent control group
Treatment Post test
Introducing Computer education to improve staff morale

63. 3. One Group Pretest-Posttest Design
In this design the experimental group is
expected to serve as a comparison group. Pretest
and posttest scores are used to find the efficiency
of the treatment.
Experimental Group
Pre-test Treatment Post test
•Effectiveness pelvic floor muscles exercises in
control of incontinence of urine.
•Effectiveness of infection control policy to
decrease infection in postnatal ward.

64. 4. PRE-TEST & POSTTEST DESIGNS WITH
A COMPARISON GROUP
In this design the comparison group
is not randomly selected. The
analysis is made on examining the
differences between comparison
group and experimental group
pretest, between pretest and post
test, between comparison group and
experimental group posttest.

65. Experimental group
Pre- test Treatment Post-test
Non equivalent control group
Pre-test Post-test
Example:
Effectiveness of education on partograph in
assessing labour progress among nurses
working in labour rooms

66. INTURRUPTED TIME SERIES DESIGN
It is similar to descriptive time series design
except that a treatment is applied at s given
point in time and the outcome is measured at
different point of time In simple interrupted
time series design there is no control or
comparison group
Use of multiple methods to measure the
outcome greatly strengthen the design.
Experimental group
Pre-test T Post test
O(1)O(2) O(3) o(1) o(2) o(3)

67. EXAMPLE
Effectiveness of selected nutritional
interventions on growth and
development pattern of children
attending under fives clinic at
Omayal Achi community health centre
at Tiruvalluvar district 2006- 2008

68. Interrupted Time series designs with
a comparison group
Comparison group allows examination of
differences in trends between groups after the
treatment and of the persistence of treatment
effects overtime
Experimental group
Pre-test T Post test
o(1) o(2) o(3) o(1) o(2) o(3)
Comparison group
Pre-test T Post test
o(1)o(2) o(3) o(1) o(2) o(3)

69. ADVANTAGES & DISADVANTAGES OF
QUASI EXPERIMENTAL STUDIES
Advantages:
From the point of view of controls for
internal validity quasi experimental
designs are thought to be superior to pre
experimental design.
Disadvantages:
Cannot test causal hypothesis
Do little to ensure external generalizability.