2. Research?
Research is the systemic collection,
analysis and interpretation of data to
answer a certain question or solve a
problem.
3. Research design
Decisions regarding what, where, when,
how much, by what means concerning an
inquiry or a research study constitute a
research design
pattern, scheme, or plan to collect evidence
Depends on the objective of the proposed
study
4. Function – To permit valid conclusion which
should be justified and unbaised
Blue print of study
6. Research design have following
parts
Sampling design
Observational design
Statistical design
Operational design
7. Samplingdesigns
Which deals with the methods of selecting items
to be observed for the study
Observational design
Which relates to the condition under which the
observation are to be create
8. Statistical design
Which concern the question of the of How
the information and data gathered are to be
analyzed ?
Operational design
Which deals with techniques by which
the procedures satisfied in sampling .
9.
10. Study design
Descriptive
Case study
Case Series
Surveys
Analytical
Prospective
Cross
sectional
Retrospectiv
e
Controlled
Randomized
Non
randomized
Non
controlled
Observational Experimental
11. Observational studies
Based on naturally occurring events
Observes and measures the
characteristics of interest to the study
Record based studies
12. Does not intervene or control the
factors related to exposure or outcome
Descriptive studies
Analytical studies
13. Descriptive study
Study is designed primarily to describe
what is going on or what exists
Involves describing the characteristics of a
particular situation, event and case in term
of time, place and person
14. Does not seek explanation or causes nor
tries to find which group is better relative to
other
Can also generate hypothesis regarding
aetiology of health condition
Can be designed to test a hypothesis
15. Helps to assess the type of diseases
prevalent in various groups and their load in
a community
Provide baseline data to launch a
programme and can measure achievements
made
16. Also good to study relationships ( systolic
and diastolic blood pressure)
Can be carried out on a large or small scale
Eg: Estimating prevalence of blindness in
cataract cases
18. Case study
A case study is defined as the use of a single
person in a research study.
Generally describes features of a new
disease entity
In clinical medicine the characteristics of so
far unrecognized illness may be documented
as a case study
19. First step toward building up a clinical
picture of that illness
Can lead to a hypothesis
20. It allows to gain a lot of in-depth, detailed
information due to the close examination of
single case
Disadvantage - might not be true for other
21. Case series
Series of case study form case-series
Objective and brief report of a clinical
characteristics or outcome from a group of
clinical subjects
lead to the generation of hypotheses
22. Advantages:
1. Easy to write.
2. The observations can be extremely useful to
other investigators.
23. Disadvantages:
1. Susceptible to many biases.
2. They are not able for conclusive decisions
3. Unrepresentativeness of subjects
4. Lack of control group
25. Disadvantage:
1. It's difficult to truly test the impact of
certain variables when all people are doing
is filling out a survey
2. Some people might not be honest in their
survey responses.
26. Analytical study
Study designed to look at the relationships
or associations between two or more
variables
EXPLANATORY STUDY
To test hypothesis
27. Antecedent
An antecedent is a precursor such as an
exposure or a risk factor suspected to affect
the disease
Other terms - Cause , predisposing factor
and determinant
28. Outcome
Outcome could be a health state, recovery,
side effect, death or any other event of
interest
This is a consequence and must necessarily
occur after the antecedent
Other terms - Effect and result
29. Prospective study
Antecedents are assessed prior to the
outcome
Since outcome occurs after the antecedent,
follow up is essential
Umbrella term includes cohort, longitudinal
and follow up study
32. Cohort study
Word cohort has its origin in the Latin
cohors
Refers to a group of warriors and gives
notion of a group of persons proceeding
together in time( same statistical
characteristic )
33. A cohort is a group of people who have
something in common and who remain
part of a group over an extended time
Incidence study
“ What will happen?”.
34. Cohort study (Follow-up Studies)
Groups of people having similar attribute (cohort)
with & without a particular exposure, or an entire
community, or a random sample of a community
are selected for the study, enrolled & followed up
over time to determine their disease rates
Disease rates of exposed subjects are compared
with rates of an unexposed group or a group with
low exposure or with registry rates
35. Advantages:
1. Opportunity to measure risk factors before
disease occurs: evidence of causality
2. Can study multiple diseases outcomes
3. Can yield incidence rate as well as relative
risk estimates.
4. Good when exposure is rare
5. Minimizes selection and information bias
36. Disadvantages:
1. Expensive and inefficient for studying rare
outcomes
2. Often need long follow-up period and/or a
very large population
3. Losses to follow-up can affect validity of
findings
4. Ineffective for rare diseases
5. Expensive
6. Ethical issues
37. Longitudinal study
Another version of prospective study
When observation or measurements are
repeatedly made at several points of time
Repeated measures study
38. Longitudinal Study
Multiple points of data collection from the same
population
Initial point of
Data collection
(Present) Follow ups (Future)
39. Cross sectional
May be descriptive or analytic
Prevalence study/ Instantaneous study/
Simultaneous study
Examine the relationship between a disease and
an exposure among individuals in a defined
population at a point in time.
“What is happening?”
40. Antecedent and outcome are observed at the
same time
Also appropiate to generate hypothesis
regarding aetiology
Subsequently tested by a case control or a
prospective study
42. Advantages:
1. Useful to know the burden of a disease in a
group – prevalence rate can be obtained
2. Cheap and fast
3. Useful to evaluate diagnostic procedure
4. To study common risk factors and
outcomes
43. Disadvantages:
1. Population little willing to collaborate
2. Doesn’t tell the flow of events
3. Only shows association between factor and
disease studied
4. It is not useful to search causes of the
outcome
44. 5. It measure at a point of time therefore
mostly it is useful to study chronic diseases
6. Confounders may be unequally distributed
7. Group sizes may be unequal
8. Recall bias
45. Retrospective study
First assessed outcome and antecedents are
subsequently assessed
Outcome is already known and antecedent is
obtained either from records or enquiry
46. Cases and control are assembled
Information about their past exposure or risk
factors is collected
48. Case control design
Dominant format of retrospective study
Subjects with or without disease are
investigated for past exposure
49. Case- suffering from disease or have
interested health condition
Control – without particular health condition
“ What happened?”
50. Advantages:
1. Allows examination of several risk factors
2. Can study long-term effects of an exposure
in short period of time
3. Use fewer subjects,
4. Relatively quick and relatively less
expensive
5. Suitable for rare diseases
51. Disadvantages:
1. Selection of an appropriate control group
can be difficult
2. Recall bias: retrospective nature
3. Cannot tell about incidence or prevalence
4. Difficult to establish time relationship
between exposure and outcome
52. Choice of the wrong control group ~ selection
bias
Cases may over-report past exposures ~
information bias
53. Case control study
53
Comparative study done by involving two
population, i.e., case and control
This permits estimation of odds ratios (but
not of attributable risks)
Allowance is made for potential
confounding factors by measuring them and
making appropriate adjustments in the
analysis.
55. Case selection
Clinic/hospital records or staff
Death records
Special clinical exams or symptom/disease
questionnaire surveys
Special disease registries
56. Control selection
Other hospital/clinic patients (well or will)
General population registers (lists of
residents in a region)
People living in the same neighborhood as
cases
People with “other diseases” in disease
registries
57. Matching
57
Defined as the process by which we select
controls in such a way that they are similar
to cases with regards to certain pertinent
selected variables which are known to
influence the outcome of disease and
which, if not adequately matched for
comparability, could confound the results.
58. 58
A confounding factor is one which is
associated with exposure and disease, and
is distributed unequally in study and control
groups
It also independent risk factor to produce
the disease. e.g smoking works as
confounding in study of the role of alcohol
in duodenal cancer.
59. Measurement of exposure
59
Obtain data related to the exposure with risk
factors of the disease under study. The data
can be obtaining by:
Interviews
Using questionnaire
Studying past records of cases form
hospital, other health institutions and
employment records.
60. Analysis
60
Odds Ratio: The ratio of probability of
getting disease with that of not getting
disease is Odds ratio.
Ratio of the odds of developing disease in
the exposed and the unexposed = a/b c/d
= ad/bc
Odds ratio is an approximation of Risk
Ratio in rare diseases.
61. Nested case control design
Combine cohort and case control features
Since case control setup is nested within a
cohort
Eg: cohort of persons of age 40-44 years
who are followed up for 15 years for
development of cataract
Case- develop cataract
Matched control – did not develop cataract
64. Basis Cohort Cross
sectional
Case
control
Main
antecedent
Outcome
Recruitment
of subject
Definition of
case
Known
Elicited
Basis of
antecedent
Subject with
specified
antecedent
Elicited
Elicited
Neither
outcome nor
antecedent
Any subject
in defined
population
Elicited
Known
Basis of
outcome
Subject with
specified
outcome
66. Basis Cohort Cross
sectional
Case
control
To determine
whether
exposure
preceded
disease
If all factors are
not known
Time and money
Best
Best
Most
expensiv
e
Not
appropiate
Less
appropiate
In between
Not
appropiate
Not
Appropiate
Least
expensive
67. Experimental study
Require deliberate human intervention to
change the course of events
Often infeasible because of difficulties
enrolling participants, high costs, and big
ethical issues,
To prove hypothesis
68. Objectives
To provide scientific proof of etiological
factors which may permit the modification
or control of those disease
To provide a method of measuring the
effectiveness and efficiency of health
services for the prevention, control and
treatment of disease and improve the health
of the community
69. Usually compared two groups
One group in which intervention takes place
Another group that remained untouched
70. Clinical Trials Studies (experimental
studies)
Involve humans are called clinical trials
studies because their purpose is to draw
conclusions about a particular procedure or
treatment
used for evaluating the effectiveness of an
intervention (therapy research questions).
75. Controlled trials are studies in which the
experimental drug or procedure is compared
with another drug or procedure as usually
previously accepted or placebo treatment.
Uncontrolled trials are studies in which the
experimental drug or procedure is described
being not compared with another treatment.
76. a) Randomized Controlled
Trials
Provides the strongest evidence for
concluding causation
It provides the best insurance that the result
was due to the intervention only
77. Provide that each individual has the same
chance of receiving each of the possible
interventions, so allocation of subjects in
experimental or control group is given by
chance.
Ensures that known and unknown
confounding factors are equal in both group,
(reduce bias)
78. b) Nonrandomized Controlled
Trials
Clinical trial or comparative studies with no
mention of randomization as well
Considered much weaker because they do
nothing to prevent bias in patient
assignment.
79. Field trials
In contrast to clinical trials, involve people who are
disease free but presumed to be at risk; data
collection take place ‘in the field’, usually among
non-institutionalized people in the general
population
Purpose is to prevent the occurrence of the
diseases that may occur with relatively low
frequency, field trials are often huge undertakings
involving major logistic and financial
considerations
80. Contd…
Field trial method can be used to
evaluate interventions aimed at
reducing exposure without
necessarily measuring the
occurrence of the health effects
E.g Blood lead levels in children
has shown the protection provided
by elimination of lead paint in home
81. Community trials
In this form of experiment the
treatment groups are communities
rather than individuals
Appropriate for diseases that have
their origins in social conditions,
which in turn can most easily be
influenced by intervention directed
at group behavior as well as at
82. True experimental research designs
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
Essentially consist of the following three
characteristics:
Manipulation
Control
Randomization
83. 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
84. PRE –EXPERIMENTAL RESEARCH
DESIGN
This research design is considered very
weak, because the researcher has very
little control over the experiment
Most suitable design for the beginners in
the field of experimental research
85. Type of study Ability to prove
causation
Randomised controlled
trials
Cohort studies
Case control studies
Cross sectional
studies
Strong
Moderate
Moderate
weak
86. Quantitative vs. Qualitative
Quantitative Research
is based on the
measurement of
quantity or amount.
It is applicable to
phenomenon that can
be expressed in terms
of Quantity.
• Qualitative Research
is concerned with
Qualitative
phenomena related to
quality of kind,
human behaviour,
attitudes, motives,
etc.
87. Measurement in various study designs
Prevalence
Incidence
Odds ratio
Relative risk
Attributable risk
89. Prevalence rate
Measured by cross sectional study
Prevalence rate = No of all cases under
study at a specified time in specified
population/ No of persons in the
population at risk at a specified time X
1000
90. Incidence rate
No of new cases of a disease under study
during a specified period of time/ total
susceptible population or population at risk
of developing the disease under study during
a specified period of time X 1000
Cohort study
91. Odds ratio
A measure of effect size
Measured in case control studies
Ratio of the odds among exposed to the
odds among unexposed
OR of 1indicates that the condition or event
under study is equally likely in both groups
92. According to standard 2X2 contingency
table
Odd of disease among exposed = a/b
Odd of disease among unexposed = c/d
OR = (a/b) / (c/d) = ad/ bc
93. Geater than 1 indicates that the condition or
events is more likely in the first group
Less than 1 indicates that the condition or
event is less likely in the first group
OR increases strength of association also
increases
94. Relativerisk / Riskratio
Risk of an event ( developing disease ) relative to
exposure
A ratio of the probability of the event occuring in the
exposed group versus a non exposed group
According to standard 2X2 contingency table
Risk of disease among exposed = a/a+b
95. Risk of disease among unexposed = c/c+d
RR = risk among exposed / risk among
unexposed
For null hypothesis, risk ration will be equal
to 1
96. RR more than one shows an association
Weak association RR >1 and < 2
Moderate to strong RR = 2 – 4
Very strong RR > 4
97. Attribute risk / risk difference
Simply a rate of disease in the exposed
people minus the rate in the unexposed
people
According to standard 2X2 contingency
table
Risk among exposed – risk among non
exposed
98. Risk of disease among exposed = a/ a+b
Risk of disease among unexposed = c/c+d
AR = risk among exposed - risk among
unexposed
For null hypothesis, AR = 0
99. References
Basis methods of medical research
A. Indranarayan, 3rd edition
Previous presentation
Internet
Research methodology for
health professionals
RC Goyal
Park’s textbook of Preventive and social
medicine, 22nd edition
