3. Research design
It is master plan specifying the methods and
procedures for following for collecting and
analyzing the needed information in a research
4. Experimental research design
…the researcher selects participants and divides
them into two or more groups having similar
characteristics and, then, applies the
treatment(s) to the groups and measures the
effects upon the groups
5. Uniqueness of experimental
• Experimental Research is unique in two
1) Only type of research that attempts to influence a
2) Best type of research for testing hypotheses about
• Experimental Research looks at the following
• Independent variable (treatment)
• Dependent variable (outcome)
6. Major Characteristics of
• The researcher manipulates the independent variable.
• They decide the nature and the extent of the
• After the treatment has been administered,
researchers observe or measure the groups receiving
the treatments to see if they differ.
• Experimental research enables researchers to go
beyond description and prediction, and attempt to
determine what caused effects.
7. Essential Characteristics of
Comparison of Groups:
• The experimental group receives a treatment of some sort while
the control group receives no treatment.
• Enables the researcher to determine whether the treatment has
had an effect or whether one treatment is more effective than
Manipulation of the Independent Variable:
• The researcher deliberately and directly determines what forms the
independent variable will take and which group will get which form.
8. Essential Characteristics of
• Random assignment is similar but not identical to random selection.
• Random assignment means that every individual who is
participating in the experiment has an equal chance of being
assigned to any of the experimental or control groups.
• Random selection means that every member of a population has an
equal chance of being selected to be a member of the sample.
• Three things occur with random assignments of subjects:
1) It takes place before the experiment begins
2) Process of assigning the groups takes place
3) Groups should be equivalent
9. Simple Random Sample
Every subset of a specified size n from the
population has an equal chance of being
10. Stratified Random Sample
The population is divided into two or more
groups called strata, according to some
criterion, such as geographic location, grade
level, age, or income, and subsamples are
randomly selected from each strata.
11. Cluster Sample
The population is divided into subgroups
(clusters) like families. A simple random
sample is taken of the subgroups and then all
members of the cluster selected are surveyed.
13. Types of Designs
The basic structure of a research study . . .
particularly relevant to experimental research
Types of experimental designs (Campbell & Stanley,
•One shot case design
•One group pretest-
•Limited control over
•No randomization and
•Non randomized block
•Time series design
•Absence of either
•Post –test only control
•Pre –test– posttest
control group design
•Cross over design
•Presence of control
a concept (e.g., intelligence, height, aptitude) that
can assume any one of a range of values
Independent variable - an activity of
characteristic believed to make a difference with
respect to some behavior
Ex - experimental variable, active variable, cause,
Dependent variable - the change or difference
occurring a result of the independent variable
Ex- Assigned variable, effect, outcome, posttest
16. Steps in conducting
Decide if an experiment addresses the
Form hypotheses to test cause-effect
Select an experimental treatment and
Identify study participants choose a type of
Conduct the experiment
Organize and analyze the data
Develop an experimental research report
17. The concept of validity…the experiment tests the
variable(s) that it purports to test
Threats to validity…
Internal: factors other than the independent
variable that affect the dependent variable(
External: factors that affect the generalizability of
the study to groups and settings beyond those of the
18. Threats of internal validity
Maturation of subjects
Selection bias – maturation interaction
Some event beside the experimental treatment
occurs during the course of the study , and this
event even influence dependent variable.
20. Maturation of subjects
Experimental research is carried on long
period of time over a group of subjects there
may be changes in the subjects in different
Increase in height, weight.
Ex. Nutritional protocol on height & weight of
Effect of taking a pretest of subjects’
performance of post test.
The effect of taking a pretest may sensitize an
individual and improve the score of the post
Individuals generally score higher during
second test regardless of treatment.
27. Reactive effect of pretest
Effect of pretest occurs when subjects have
been sensitized to the treatment because of
Ex – pretest may sensitize to learn about HIV/
AIDS irrespective of health education is
28. Novelty effect:
Treatment is new , the subjects and researchers act
People : Generalization is not applicable depending
upon the race.
Place: Generalization not possible for people living
in rural and urban area
Time : older results can not be generalized over
periods of time.
29. Most common way to eliminate
Experimental control Experimental control attempts to
predict events that will occur in the experimental setting
by neutralizing the effects of other factors.
Physical Control Gives all subjects equal exposure to
the independent variable. Controls non-experimental
variables that effect the dependent variable.
Selective Control Indirectly manipulate by selecting in
or out variables that cannot be controlled
Statistical Control Variables not conducive to physical
or selective manipulation may be controlled by statistical
30. Criteria for evaluating
Does the experiment have a powerful
Does it employ few treatment groups (e.g. only
Will participant profit from the intervention?
Is there a systematic way the researcher
derived the number of participants per group?
31. Criteria for evaluating
Were there an adequate number of
participants used in the study?
Were valid, reliable, and sensitive measures or
Did the study control for extraneous factors?
Did the researcher control for threats to
32. Types of pre experimental
The One-Shot Case Study
A single measure is recorded after the treatment
Study lacks any comparison or control of
To remedy this design, a comparison could be
made with another group.
33. The One-Group Pretest-Posttest Design
Subjects are measured before and after treatment is
Uncontrolled-for threats to internal validity exist.
To remedy this design, a comparison group could be
34. The Static-Group Comparison
Use of 2 existing, or intact groups.
Experimental group is measured after being
exposed to treatment.
Control group is measured without having been
exposed to the treatment.
35. The Static-Group Pretest-Posttest Design
Pretest is given to both groups.
“Gain” or “change” = pretest score -
Better control of subject characteristics
A pretest raises the possibility of a testing
36. Pre experimental design
Convenient to conduct in
Suitable for beginners
Weak design to establish
casual relationship between
independent and dependent
Very little control over the
Higher threat to internal
37. Characteristic of quasi
experimental research design
Manipulation of independent variable
Lack of one / two essential character of true
Quasi independent variable used instead of
true independent variable.
38. Types of quasi experimental
Nonequivalent /Non randomized control group
O X O
random assignment of intact groups that are
pretested ( O ), exposed to a treatment ( X )
and then posttested ( O )
O O O O X O O O O
a single group is pretested ( O ) repeatedly until
pretest scores are stable, exposed to a
treatment ( X ) and, then, is repeatedly
posttested ( O )
40. Characteristics of true
Manipulation – control of independent
variable by the researcher through treatment/
Control – the use of control group and
extraneous variables on the dependent
Randomization – every subject gets equal
chance being assigned to experimental and
41. Advantages Disadvantage
Most powerful design to establish
causal relationship between
independent and dependent
Cannot be replicated in studies
conducted in human begins due
Purity of the observation Many of the human variables
neither have valid measurable
criteria nor instruments to
Create conditions in a short period
of time that may take years to
Studies conducted in hospital /
community difficult to control the
Conducted in laboratory,
experimental unit, specialized
Very difficult get co operation for
42. True Experimental
• The essential ingredient of a true experiment is
random assignment of subjects to treatment groups
• Random assignments is a powerful tool for
controlling threats to internal validity
– The Randomized Posttest-only Control Group Design
• Both groups receiving different treatments
– The Randomized Pretest-Posttest Control Group
• Pretest is included in this design
– The Randomized Solomon Four-Group Design
• Four groups used, with two pre-tested and two not pre-tested
43. The Randomized Posttest-Only
Control Group Design
Experimental group tested after treatment exposure.
Control group tested at the same time without exposure
to experimental treatment.
Includes random assignment to groups.
Threats to internal validity – mortality, attitudinal,
implementation, data collector bias, location and history.
45. The Randomized Pretest-
Posttest Control Group Design
Experimental group tested before and
after treatment exposure
Control group tested at same two times
without exposure to experimental
Includes random assignment to groups.
Pretest raises the possibility of a pretest
treatment interaction threat
46. Example of a Randomized Pretest-
Posttest Control Group Design
47. The Randomized Solomon Four-
Combines pretest-posttest with control group
design and the posttest-only with control
Provides means of controlling the interactive
test effect and other sources of extraneous
Does include random assignment.
Weakness: requires a large sample.
50. Solomon four-group design
R O X1 O
R O X2 O
R X1 O
R X2 O
four groups are formed by random assignment
( R ) of participants, two groups are pretested
( O ) and two are not, one pretested and one
un pretested group receive the experimental
treatments ( X1, X2 ), each group is are
administered a posttest on the dependent
variable, and posttest scores are compared to
determine effectiveness of treatments
51. Factorial design
involve two or more independent variables
with at least one independent variable being
manipulated by the researcher
two-by-two factorial design (four cells)
2 X 2
two types of factors (e.g., method of
instruction) each of which has two levels (e.g.,
traditional vs. innovative)
55. Randomized block design
Principle of local control along with other two
principle of experimental design
subjects are first divided into groups
each group the subjects are relatively
The number of the equal in each group
Extraneous variable is fixed
57. Cross over design / repeat
Subjects exposed more than one treatment
Subjects randomly assigned to different orders
Equal distribution of character among the
58. Latin square design
very frequently used in agricultural research.
An experiment has to be made through which
the effects of five different varieties of
fertilizers on the yield of a certain crop.
out put occur depend on soil not only on the
L.S. design is used when there are two major
extraneous factors such as the varying soil
fertility and varying seeds
60. Other designs
Univariant descriptive design – the frequency
of occurrence of the phenomenon
Ex – the experience of patients suffering from
Prevalence of vitamin D deficiency among
Used to identify, describe the perception,
awareness, behavior, attitude, knowledge and
practice of people.
61. Exploratory design
Used to identify , explore and describe the
existing phenomenon and its related factors
Ex . contributing factors of sleep disturbance
among patients admitted in ICU
62. Comparative design
Comparing and contrasting two or more
sample of subjects on one or more variable
Attributes-Knowledge, perception, attitudes
Physical and psychological symptoms
Ex KAP on Vitamin D among antenatal
63. Prospective Cohort Study
Some have the
(lapse of time)
Begin enquiry here
& work forwards
Statistic = Relative Risk [RR] = (a/c) divided by (b/d)
This shows the ratio of incidence in exposed
compared to non-exposed.
RR > 1 implies a hazard;
RR < 1 implies a protective factor
95% CI are usually presented:
e.g., RR = 1.9 (95% CI 1.5, 2.3)
Note: as you begin
with people who do not
have the disease, you
can calculate incidence
but not prevalence.
(Prevalence would be
underestimated as you
Some do not (d)
64. Retrospective Case-Control Study
(who do not
Not Exposed (d)
Not Exposed (b)
Begin enquiry here
& look backwards
Statistic = Odds Ratio [OR] = (a/b) divided by (c/d)
This shows how many times more likely were the cases
to have been exposed than the controls.
OR interpreted in same way as RR
Note: as you begin
with people who already
have the disease, you
incidence or prevalence
65. Developmental research
Cross sectional design
Researcher collect data at particular point of
Ex –assessing the awareness on swine flu
among people of an area
Collect the extended period of time
follow up studies
66. Other type of trails
Pilot studies and feasibility studies– run before
a large trail take place
Screening trails – cervical cancer screening
Prevention trails – breast cancer prevention
Trails looking at causes and patterns of
Case control studies
There are several research designs and the
researcher must decide in advance of
collection and analysis of data as to which
design would prove to be more appropriate for
his research project.
68. Applying What you Have
Learned: An Experimental Study
Review the article and look for the following:
The research problem and use of quantitative
Use of the literature
The purpose statement and research
Types and procedures of data collection
Types and procedures of data analysis and
The overall report structure
Notas do Editor
Experimental research = try something and systematically observe what happens.Two basic conditions of formal experiments – 1st, at least 2 (or more) conditions or methods are compared to assess the effect of treatments (independent variable). 2nd, independent variable directly manipulated by researcher.
Experimental group receives a treatment.Control/comparison group receives no/different treatment. Become yardstick to determine whether the treatment is effective/not.Researcher actively manipulates a treatment (independent variable) – deliberately & directly determines what forms (treatment) and which group will get.Independent variables that can be manipulated – teaching method, type of counseling, learning activities, etc.Independent variables may be established in several ways – (i) one variable vs. another, (ii) presence vs. absence, (iii) varying degrees of the same form.
Intended to eliminate the threat of extraneous or additional variables.Ensures that groups formed are equivalent at the beginning of an experiment.No guarantee of equivalent groups unless both groups (experimental & control) are sufficiently large.
One group only (experimental group) that received treatment. No control/comparison group = to effectiveness cannot be measured.No pretest, researcher knows nothing about the subject before treatment thus does not know whether it is effective or not.
Pretest exist, so does nine uncontrolled-for threats (history, maturation, instrument decay, data collector characteristics, data collector bias, testing, statistical regression, attitude of subjects & implementation.Researcher would not know if any differences between pretest and posttest due to treatment given/threats.
a.k.a. nonequivalent control group designSubjects are being formed but not randomly assigned.Diagrammed shows better control (history, maturation, testing & regression) but still not a good design as the possibility of other threats (mortality, location & subject characteristics) occur.
? Better control = changed being analyzed but still remain a threat as it depends on initial performance (pretest improve or less).
? True=random assignment to treatment (independent variable) group.Random assignment best tool to control threat to internal validity.
Two groups – experimental and control/comparison group which is formed by random assignment.There are still threats but can sometimes be controlled by appropriate modifications.Important to keep clear distinction between random selection and random assignment.Random selection is intended to provide a representative sample.Random assignment is intended to equate groups and often is not accompanying by random selection.
X1 represents exposure to treatment (independent variable).O refers to the measurement of the dependent variable (outcome).R represents random assignment of individual to groups.X2 represents control group.