1. STUDY DESIGN
IN
RESEARCH
* Few jewels from ocean
Dr. Kusum Gaur
Professor, PSM
WHO Fellow IEC

2. Definition of Research
“Research is a
systematized effort
to gain new knowledge”.
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3. Steps in Research (Holy 11)
1. Collect review of literature/Situation Analysis
2. Identify and prioritize health problems
3. Decide aims & objectives
4. Planning Methodology including study design
5. Execution
6. Compilation, Classification & Presentation of data
7. Analysis
8. Test of Significance/Test of Hypothesis
9. Inferences
10. Report Writing
11. Dissemination of Report
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4. Study Design
A study design is a specific plan or protocol
for conducting the study,
which allows the investigator
to translate the conceptual hypothesis
into an operational one.
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5. Direction of Study
Backward Forward
Cross -sectional
Retrospective Prospective
3
4. Ambidirectional
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6. Decision Tree
Intervention Done
No Yes
Observational Study Experimental Study
Comparison Group Randomization
No Yes
No Yes
Descriptive Study Analytic Study
NRCT Study RCT Study
Direction of Study
E O E O
Cohort Study E = O Case-Control Study
Cross-Sectional Study
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7. Epidemiological Study Design
Observational Studies
 Descriptive Studies
Analytic
Cross-Sectional
Case-Control
Cohort
Experimental / Interventional studies
As per Control: RCT/NRCT
As per Blinding: Single /Double Blind
As per Design: Simple/Cross-over
As per Area: Field/Clinical/Lab
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8. Descriptive Studies
• Case reports
• Case series
• Population studies
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9. Descriptive Studies: Uses
• Hypothesis generating
• Suggesting associations
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10. Descriptive Type of Observational Study
• Other Name Case-Series/Population
• Unit of Study Case/Individuals
• Study Question What is happening 
• Direction Of Inquiry
• Study Design
☻☻☻☻☻☻ desired information
☻☻☻☻☻☻ about cases/individuals is collected
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11. Case-Series …….
Advantages
• Easy to do
• Excellent at identifying unusual situation
• Good for generating hypotheses
Disadvantages
• Generally short-term
• Investigators self-select (bias!)
• no controls
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12. Analytical Observational Studies
• Cross-sectional
• Case-control
• Cohort
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13. Cross-sectional Study
• Data collected at a single point in time
• Describes associations
• Prevalence
A “Snapshot”
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14. Cross-Sectional Study
• Other Name Prevalence Study
• Unit of Study Individual
• Study Question What is happening 
• Direction of Inquiry
• Study Design Exposed
to Factor
Not
 Exposed
Diseased to Factor
Population Exposed to
 Factor
Non-
Disease Not
Exposed to
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15. Objectives of a Cross-Sectional Study
To find out association
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16. Cross-sectional Study
Sample of Population
Defined Population
Regular Not doing meditation
Meditation
Prevalence of Prevalence of
DM DM
Time Frame = Present
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17. Cross-sectional Study
E.G. Out of 1000 population if 100 were doing meditation regularly &
out of that only 2 were having DM. Remaining 900 were not doing
meditation at all, out of that 220 were having DM.
+ DM -
2 98
Meditation
+
- 220 680
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18. Cross-Sectional Study
• Strengths
– Quick
– Cheap
• Weaknesses
– Cannot establish cause-effect
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19. Case-Control Studies
 Start with people who have disease(Cases)
 Match them with controls that do not have
disease (Match Confounding)
 Look back and assess exposures
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20. Controls
A control is a standard of comparison
(confounded with variability but without
effect)
for
• Effects
• Variability
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21. Case-Control Study
• Other Name Retrospective Study
• Unit of Study Cases/Control
• Study Question What has happened 
• Direction of Inquiry= F O
• Study Design
Exposed
 Cases
Not
Exposed
Exposed
Control
Not
Exposed
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22. Objective of a Case-Control Study
To find out association
To assess Risk Ratio
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23. Case-Control Study
Cases
Regular Meditation
Patients with DM
No Meditation
Controls
Regular Meditation
Persons w/o DM
No Meditation
Past Present
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24. The logic of Case-Control Studies
Cases differ from controls only in having the
disease
If exposure does not predispose to having the
disease, then exposure should be equally
distributed between the cases and controls.
 The extent of greater previous exposure among
the cases reflects the increased risk that
exposure confers
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25. Case-Control Studies: Strengths
• Good for rare outcomes: cancer
• Can examine relation of exposures to disease
• Useful to generate hypothesis
• Fast
• Cheap
• Provides Odds Ratio
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26. Case-Control Studies: Weaknesses
• Cannot measure
– Incidence
– Prevalence
– Relative Risk
• Can only study one outcome
• High susceptibility to bias
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27. Cohort Study
• Begin with disease-free individuals
• Classify patients as exposed/unexposed
• Record outcomes in both groups
• Compare outcomes using relative risk
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28. Cohort Study
• Other Name Prospective Study / Follow-up Study/Incidence Study
• Unit of Study Individual
• Study Question What is happening 
• Direction of InquiryF O
Diseased
• Study Design
• Exposed to
Factor
Not Non
Diseased
Cohort
Cohort Diseased
Not
Exposed to
Factor
Non-Diseased
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29. Logic of Cohort Study
Cohort is a group of persons sharing a
common characteristics
Differences in the rate at which exposed and
control subjects contract a disease is due to
the differences in exposure, since others are
known and similar.
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30. Cohort Study
 Prospective (usually)
 Controlled
 Can determine causes and incidence of
diseases as well as identify risk factors
 Generally expensive, time consuming and difficult
to carry out
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31. Steps for Cohort Study
Identify geographically defined group
Identify exposed subjects and not exposed
subjects
Follow over a specific time
Record the fraction in each group who
develop the condition of interest
Compare these fractions using RR, AR or OR
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32. Objectives of a Cohort Study
 To find out association
To assess Risk Ratio
To find out Relative Risk
To find out Attributed Risk
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33. Prospective Cohort Study
DM
No Meditation
No DM
Cohort
DM
Regular
Meditation No DM
Present Future
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34. Cohort Study: Strengths
• Can measure multiple outcomes
• Can adjust for confounding variables
• Can calculate Attributed Risk
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35. Cohort Study: Weaknesses
• Expensive
• Time consuming
• Cannot study rare outcomes
• Confounding variables
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36. Measurements of Association
Cohort Study Case Control Study
•Significance Test •Significance Test
•Relative Risk •OR
•Attributable Risk
•OR
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37. Measures of Association
Significance Test – to test significance of difference
in exposure between control and Cases
Odds ratio - ratio of the odds of contracting
disease in given exposure
Relative Risk – Ratio between incidence among
exposed and incidence among non-exposed
Attributed Risk – percentage of difference between
incidence among exposed and non-exposed with
incidence among exposed
RR or OR of 1 indicate no effect of exposure (equal odds)
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38. ‘Z’ Score of Exposure Rates
Cases control
Exposed a b
a x 1oo
Exposure Rates = in Cases Non- c d
exposed
(P2) a+c
b x 1oo
Exposure Rates = in Controls P2 – P1
(P1) b+d Z Score =
SEDP
P1 Q 1 P 2 Q 2
SEDP = ------------- + --------
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N1 N2

39. ad
ODD’s Ratio = Times
bc
Incidence among Exposed
RR = Times
Incidence among Non-Exposed
a/a+b a (c+d)
= =
c/c+d c (a+b)
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40. Attributed Risk
(Incidence among Exposed - Incidence among Non-Exposed)
AR = x 100
Incidence among Exposed
a
Incidence among Exposed= x 100
a+b
c
Incidence among Non-Exposed= x 100
c+d
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41. Experimental Studies
Clinical trials provide the “gold standard” of
determining the relationship between
factor and the event
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42. Types of Experimental Study
As per Randomization:
• Randomized Control Trials (RCT)
• Concurrent Parallel Design (RCT)
• Sequential RCT Design
• RCT with External Control
• Non – Randomized Trials
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43. Types of Experimental Study….
As per Construction:
• Simple
• Cross-Over Study Design
As per Study Area:
• Field Trials
• Clinical Trials
• Lab. Trials
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44. Quality of Experimental Study
• Randomization
• Blinding
• Control
• Cross-Over
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45. Controls in Clinical Trials
A clinical trial is a comparative, prospective
experiment conducted in human subjects
• Historical controls are better than no controls
• Patients can serve as own controls - This is
usually beneficial as the comparison removes
patient differences
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46. Blinding
Good practice: factors that can affect the
evaluation of outcome should not be permitted
to influence the evaluation process
Single-blind
Patient or evaluator (either of one) is blinded as
to intervention
Double-blind design
Neither patient nor outcome evaluator knows
Rx to which patient was assigned
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47. Randomized Control Trials
(RCT)
• Before and After Comparison
• Comparison with Placebo
• Comparison Of two medicine/procedure/tests
• Comparison Of > two medicine/procedure/tests
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48. Experimental Study
• Other Name Intervention Study
• Objective To know the effect of intervention
• Unit of Study Individual meeting entry criteria
• Study Question What is happening after intervention in both
groups 
• Direction of Inquiry I E
• Study Design 1(Intervention with Placebo) Positive
Outcome
Group 1/cases Intervention
Negative
Outcome
Positive
Outcome
Group
Placebo
2/control
Negative
Outcome
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49. Clinical Trial
R Treatment
a Outcomes
Group
n
d
Study o
Population m
i
z Outcomes
e Control Group
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50. Intervention Study - Design 2
(Comparison of Effect of Two Interventions)
Cases
Meeting
Entry criteria
Group - 1 Group -2
Intervention -1 Intervention Intervention - 2
Positive Negative Positive
Outcome Negative
Outcome Outcome Outcome
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51. Cross Over Design
Group -1 Cases Group-2
Meeting
Entry
criteria Intervention - 2
Intervention - 1
Positive Negative
Positive Negative Outcome
Outcome Outcome
Outcome
Group -1
Group -2 Crossover
Intervention -2
Intervention -1
Positive Negative
Positive Negative
Outcome
Outcome Outcome
Outcome
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52. Other Types of Experimental Study
• Quincy Experimental Study
• Block Experimental Study
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53. Quincy Experimental Study
Cases
Meeting
Entry criteria
Group - 1 Group -2
Intervention Intervention No Intervention
Positive Negative Positive
Outcome Negative
Outcome Outcome Outcome
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54. Block Experimental Study
Cases
Meeting
Entry criteria
Group -3
Group - 1
Group -2
Intervention Intervention-3
Intervention -1 Intervention
Intervention-2
Positive Positive Negative
Negative
Outcome Outcome Outcome Outcome
Positive Negative
Outcome Outcome
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55. Steps of Experimental Study
Drawing up a Protocol
Reference Population
Sample Population
Exclusions
Randomization
Experimental Group Control Group
Manipulation/Intervention
Follow - up
12/08/2012 Assessment of Outcome
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56. Ideal Study Design for established causality
Ethical Issues

57. STUDY QUESTIONS AND APPROPRIATE DESIGNS
Type of Question Appropriate Study Design
Burden of illness Field Surveys
- Prevalence Cross Sectional Survey
- Incidence Longitudinal survey
Causation, Risk & Prognosis Case Control Study,
Cohort study, RCT
Treatment Efficacy Randomized Controlled study
Diagnostic Test Evaluation Randomized Controlled study
Cost Effectiveness Randomized Controlled study
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58. Hierarchy of Epidemiological Study Design
Establish Causality RCT
Cohort
Case Control
Cross-Sectional
Case Series
Generate Hypothesis Case Report
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