types of research design

1. EXPERIMEN RESEARCH
DESIGN
By
Nimra farooq
Roll no# f16-0714
Bs 5 - psychology
Submitted to: Ma’am Andleeb

2. INTRODUCTION…
 Experimental is most scientifically
sophisticated research method.
 It is defined as ‘observation under controlled
conditions’.
 Experimental research design are concerned
with examination of the effect of independent
variable on the dependent variable, where the
independent variable is manipulated through
treatment or intervention(s), & the effect of
those interventions is observed on the
dependant variable

3. TRUE
EXPERIMENTAL
DESIGN

4. CONCEPT…
 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

5. ESSENTIAL CHARACTERISTICS…
 A true experimental research design must
essentially consist of the following three
characteristics:
Manipulation
Control
Randomization

6. MANIPULATION:
 Manipulation refers to conscious control of
the independent variable by the
researcher through treatment or
intervention(s) to observe its effect on the
dependent variable.
 In other words, it is a conscious act by the
researcher, where he or she varies the
independent variable & observes the
effect that manipulation has on the
dependant variable of interest.

7. COUNT…
 For example, a researcher is conducting a
study on efficacy of cholrhexidine mouthwash
on the prevention of ventilator-associated
pneumonia (VAP) among patients admitted in
ICUs.
In this example, chlorhexidine mouthwash is
the dependent variable, which is manipulated
by the researcher, & is used as an
intervention for the experimental group, while
the control group is kept deprived of it to
observe its effect on the incidence of VAP

8. CONTROL:
 Control is another essential element of true
experimental design.
Control refers to use of control group &
controlling the effects of extraneous
variables on the dependent variable in
which researcher is interested.
The subject in the control & experimental
groups are similar in number &
characteristics, but the subject in the control
group receive no experimental treatment or
any intervention at all.

9. COUNT…
 The experimental group receives the planned
treatment or intervention & a comparison is
made with the control group to observe the
effect of this treatment or intervention.
 Generally in health care & nursing research, it
is not ethically feasible keep a control group
deprived of interventions; however, existing
conventional method of interventions may be
compared with experimental interventions.

10. RANDOMIZATION:
 Randomization means that every subject has an equal
chance of being assigned to experimental or of study
subjects on a random basis.
 Through random assignment of subject under
experimental or control group, chances of systemic bias
is eliminated.
 Randomization is used in true experimental research
design to minimize the threat of internal validity of the
study & to eliminate the effect of extraneous variables on
dependent variables.
 Through randomization, on average the characteristics of
the subject in experimental & control groups are similar,
thus influence of extraneous variables on dependant
variable is eliminated by dispersing the variability of the
subject characteristics equally in both the groups.

11. COUNT…
METHODS OF RANDOMIZATION:
 Random assignment of subject may done with simple flip
of a coin for each subject; if coin lands on its ‘head’,
subjects are assigned to first group & with ‘tail’ subjects
are assigned to control group.
 Another possible method is to write the names of the
subjects on slips of paper & put the slips into a bowl &
then draw lots. The first designated numbers of subjects
are placed in one group, & rest are assigned under
another group.
 Thirdly a random table may be used to facilitate the
randomization process. In this method, blind-folded
subjects choose a number from a table of number
horizontally (row) or vertically (columns), till a requisite
number is reached for both experimental & control
groups. Computer-assisted random sequences also may
be used for the random assignment of the subjects

12. TYPES OF THRUE EXPERIEMNTAL DESIGN
True Experiential Design
Post-test
only
Pretest
post-test
only
Randomized
block
Solomon 4
groups Factorial
Crossover

13. POST-TEST-ONLY CONTROL DESIGN:
 Composed of two randomly assigned group, i.e.
experimental & control, but neither of which is pretested
before the implementation of treatment on the
experimental group.
 In addition, while treatment is implement on the
experimental group only, post-test observation is carried
out on both the group to assess the effect of
manipulation.
 This design can be helpful in situations where it is not
possible to pretest the subjects.
 For example, to study the effect of an educational
intervention related to urinary incontinence on the
subsequent help-seeking behavior of older adults.

14. COUNT…
Random
assignment
Control group
Treatment Post-test
Post-test
Exp. group

15. RETEST-POST-TEST-ONLY DESIGN
 In this research designs, subjects are randomly assigned
to either the experimental pr the control group.
 The effect of the dependent variable on both the groups
is seen before the treatment (pretest).
 Later, the treatment is carried out on experimental group
only, & after-treatment observation of dependant variable
is made on both the groups to examine the effect of the
manipulation of independent variable on dependant
variable.
 For example, such a design could be used for ‘an
experimental study to assess the effectiveness of
cognitive behavioral therapy interventions for patients
with breast cancer.

16. COUNT…
Random
assignment
Control
group
Treatment
Post-
test
Post-test
Exp.
group
Pre-
test
Pre-
test

17. SOLOMON FOUR-GROUP DESIGN
 There are two experimental groups (experimental group
1 & experimental group 2) & two control groups (control
group 1 & control group 2).
 Initially, the investigator randomly assigns subjects to the
four groups.
 Out of the four groups, only experimental group 1 &
control group1 receives the pretest, followed by the
treatment to the experimental group 1 & experimental
group 2.
 Finally, all the four groups receive post-test, where the
effects of the dependant variables of the study are
observed & comparison is made of the four groups to
assess the effect of independent variable (experimental
treatment) on the dependant variable

18. COUNT…
 in this, experimental group 2 was observed at
one occasion, & that score should be similar to
average scores of those in experimental &
control groups.
 To estimate the amount of change in
experimental & control group 2, the average
test scores of experimental & control groups 1
are used as baseline
 The Solomon four-group design is believed to
be most prestigious experimental research
design, because it minimizes the threat to
internal & external validity.

19. COUNT…
Random
assignment
Control Group 1
Exp. Group 1
Exp. Group 1
Control Group 1
pretest
Pretest
Treatment
Treatment
Post-test
Post-test
Post-test
Post-test

20. COUNT…
 Example. Third graders are randomly assigned
to 1 of 4 groups. The
“knowledge of language” is measured in groups 1
and 2. Groups 1 and 3 are
given a special study on the language learning.
When the special study is
over, all four groups are tested.

21. COUNT…
 - the first and the second groups are retested;
- the first and the third groups are exposed to the
treatment,
and the second and the fourth groups are taken as
control
groups;
- all four groups are posttested.
This design provides the best result but it requires a
large
sample so that enough subjects could be assigned to
four
groups.
When the sample is large, administering the tests
becomes
difficult, time and energy consuming.

22. FACTORIAL DESIGN
 In factorial design, researcher manipulates two or more
independent variables simultaneously to observe their effects on
the dependant 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 mouth care on prevention of VAP 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 (α) refers to the independent variables or the
type of experimental treatments, & the second number (β) refers
to the level or frequency of the treatment.

23. FACTORIAL DESIGN

24. QUASI –
EXPERIMENTAL
RESEARCH
DESIGN

25. QUASI-EXPERIMENTAL DESIGNS
 The term quasi- (pronounced kwahz-eye) means almost, near,
partial, pseudo, or somewhat.
 Quasi-experimental designs are used when true
experiments cannot be done. A common problem in
educational research is the unwillingness of educational
administrators to allow the random
selection of students out of classes for experimental samples.
 Without randomization, there are no true experiments. So,
several designs have been developed for these situations that
are “almost true experiments,” or quasi-experimental designs.
 We’ll look at three:
 the time series
 the nonequivalent control group design,
 the counterbalanced design.

26. CONTINUE..
 Quasi-experimental research design involves the
manipulation of independent variable to observe to effect
on dependant variable, but it lacks at least one of the two
characteristics of the true experimental design;
randomization or a control group.
In other words, quasi-experimental designs have an
element of manipulation but lack at least one of the other
two properties that characterize true experiments;
randomization or a control group.
Quasi-experimental designs 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.

27. MAIN CHARACTERISTICS
 Manipulation of the independent variables to
observe the effects on the dependant 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 is not manipulates in
complete controller situations.

28. TYPES OF QUASI-EXPERIMENTAL
DESIGN
 Nonrandomized control group design
 Time-series design

29. NONRANDOMIZED CONTROL GROUP
DESIGN
 It is also known as the ‘nonequivalent control group
design’.
 This design is identical to the pretest-posttest control
group design, except there is no random assignment of
subjects in experimental & control groups.
 In this design, experimental & control groups are
selected without randomization, & dependent variables
are observed in experimental as well as control groups
before the intervention.
 Later, the experimental group receives treatment & after
that posttest observation of dependant variables is
carried out for both the groups to assess the effect of
treatment on experiment group

30. COUNT…
 For example, this method was used to study ‘the effects of
integrated self esteem on quality of work of participents: a
quasi experiment’.
 A nonequivalent pretest-posttest control group design was
used in
this study.
 Data was collected by through a questionnaire.
 Regarding the effects of the intervention on the quality of work
factors, the result included an increase of social support by
supervision.
 The intervention on the psychosomatic wards was
unsuccessful,
through the introduction of integrated care on the somatic
wards
was fairly successful.

31. High
Self-Esteem
Group
Low
Self-Esteem
Group
17 12
19 10
16 14
12 15
17 13
18 12
15 11
16 13
Any Difference
Variable 1: Self-Esteem
not manipulated but
used to
define two groups of
participants
Variable 2: Academic
Performance
(the Dependent Variable)
Measured in each of the
two groups
Participant Variable
Self-Esteem
Variable
Academic
Performance
A 84 16
B 72 10
C 90 19
D 68 13
E 77 16
F 81 12
G 85 17
H 78 13

32. TIME-SERIES DESIGN
 This design is useful when the experimenter wants to
measure the effects of a treatment over a long period of
time.
 The experimenter would continue to administer the
treatment & measure the effects a number of times
during the course of the experiment.
 Generally it is a single-subject research, in which the
researcher carries out an experiment on an individual or
on a small number of individuals, by alternating between
administering & then withdrawing the treatment to
determine the effectiveness of the intervention.
Exp.
group 01 02 03 Treatment 01 02 03

33. COUNT…
 A researcher might assess pain levels of a
group of patients with low-back pain. After 3
weeks of pain assessment, subjects are
taught special exercises to reduce that pain.
During the next 3 weeks, pain levels would
again be measured.
 Measuring a child’s school performance on
a weekly basis, & then introducing a new
teaching technique. Then again measuring
on a weekly basis

34. O1 O2 O3 O4 O5 O6
Observations
Before Treatment
Observations
After Treatment
Treatment
Averagescore
A Time Series Study with Multiple Observations Before
and After Treatment

36. ADVANTAGES OF QUASI-
EXPERIMENTAL DESIGN
 Quasi-experimental designs are more frequently used
because they are more practical & feasible to conduct
research studies in nursing, where in the absence of a
large sample size, randomization &/ or availability of
control groups are not always possible.
 This design is more suitable for real-world natural
setting than true experimental research designs.
 It allows researchers to evaluate the impact of quasi
independent variables under naturally occurring
conditions.
 It may be able to establishing casual relationship.
Wherein some of the hypotheses are practically
answered through this design only

37. DISADVANTAGES OF QUASI-
EXPERIMENTAL DESIGN
 There is no control over extraneous
variables influencing the dependant
variables.
 The absence of a control group or lack of
control over the research setting makes the
results of this design less reliable & weak for
the establishment of casual relationship
between independent & dependant
variables.

38. Thank
You