This document discusses different types of observational studies and experimental trials used in research methodology. It defines observational studies as those that involve collecting data without intervening or altering the course of events. The main types of observational studies covered are case-control studies, cohort studies, cross-sectional studies, and ecological studies. Experimental trials involve manipulating a variable and measuring the effects. Randomized controlled trials are described as the gold standard for determining causation. Key aspects of randomized controlled trial design and methodology are outlined.

2. INTRODUCTION:
Research Methodology is defined as highly
intellectual human activity used in the investigation
of nature and matter & deals specifically with the
manner in which data is collected, analyzed &
interpreted.
A system of models, procedure and techniques used
to find the result of a research problem is called
RESEARCH METHODOLOGY.

5. Observational study involves
collection of data by carefully
watching and recording behavior
as it occurs.
OBSERVATIONAL STUDY:

6. The four main types of observational
studies are
Case-control study.
Cohort study.
Cross-sectional study.
Ecological study.
 TYPES OF OBSERVATIONAL
STUDY:

7.  A study that compares patients who have a disease or outcome
of interest (cases) with patients who do not have the disease or
outcome (controls), and looks back retrospectively to compare
how frequently the exposure to a risk factor is present in each
group to determine the relationship between the risk factor and
the disease.
 Case control studies are observational because no intervention is
attempted and no attempt is made to alter the course of the
disease. The goal is to retrospectively determine the exposure
to the risk factor of interest from each of the two groups of
individuals: cases and controls. These studies are designed to
estimate odds.
 Case control studies are also known as "retrospective studies"
and "case-referent studies."
CASE CONTROL STUDY:

8.  CASE-CONTROL STUDY
DESING:

9. • Good for studying rare conditions or diseases.
• Less time needed to conduct the study because the
condition or disease has already occurred.
• Lets you simultaneously look at multiple risk factors.
• Useful as initial studies to establish an association.
• Can answer questions that could not be answered
through other study designs.
ADVANTAGES OF
CASE CONTROL STUDY:

10. • Retrospective studies have more problems with data
quality because they rely on memory and people with
a condition will be more motivated to recall risk
factors (also called recall bias).
• Not good for evaluating diagnostic tests because it’s
already clear that the cases have the condition and
the controls do not.
• It can be difficult to find a suitable control group.
DISADVANTAGES OF
CASE CONTROL STUDY:

11. • The word cohort derived from Latin “cohorts”
meaning enclosure, company, or crowd.
• It is a type of analytical study which is
undertaken to obtained additional evidence to
refute or support existence of association
association between suspected case and disease.
 COHORT STUDY:

12. • 1. Prospective
• 2. Retrospective
• 3. Combined -
 TYPES OF COHORT STUDY:

13.  COHORT STUDY DESING :
(prospective)

14.  COHORT STUDY DESING :
(Retrospective)

15. 1. Selection of subjects
• General population
2. Obtain data on exposure
• Clearly define exposure • How? – Direct interview – Medical examination –
Record review – Environmental survey • Classify into exposed and non-exposed •
Among exposed degree of exposure
3. Selection of comparison
• Internal comparison • External comparison • General population
4. Follow up and measure outcome
• Clearly define outcome • Periodic interview or examination • Loss to follow up –
Denial of consent – Death – Migration • Ideal follow up is >95%
5. Analysis
• Incidence of disease in exposed = • Incidence of disease in non-exposed = •
Relative risk (RR) =
 ELEMENTS OF COHORT:

16.  Incidence and RR can be calculated.
 One exposure and multiple outcomes.
 Dose response ratios.
 Recall bias reduced .
ADVANTAGES OF
COHORT STUDY:

17.  Unsuitable for rare outcomes
 Long duration
 Administrative problems
 Loss to follow up
 Selection of representative groups
 Diagnostic criteria may change over time
 Expensive
 People may alter their behavior
 Ethical problems
DISADVANTAGES OF
COHORT STUDY:

18. CROSS-SECTIONAL STUDY:
It is a type of observational study that analyzes
data collected from a population, or a
representative subset, at a specific point in time—
that is, cross-sectional data.

19.  CROSS-SECTIONAL STUDY
DESING :

20. Used to prove and/or disprove assumptions.
Not costly to perform and does not require a lot of time.
Captures a specific point in time.
Contains multiple variables at the time of the data
snapshot.
The data can be used for various types of research.
Many findings and outcomes can be analyzed to create new
theories/studies or in-depth research.
ADVANTAGES OF
CROSS-SECTIONAL STUDY:

21. • Cannot be used to analyzed behavior over a period to time.
• Does not help determine cause and effect.
• The timing of the snapshot is not guaranteed to be
representative.
• Findings can be flawed or skewed if there is a conflict of
interest with the funding source.
• May face some challenges putting together the sampling
pool based on the variables of the population being
studied.
DISADVANTAGES OF
CROSS-SECTIONAL STUDY:

22. • It is not easy to establish links between exposures and
health outcomes using individual level data
-Problems for obtaining measures of dose levels for
individuals,
-There is also often the difficulty to deal with long
latency times between exposure and diagnosis (e.g
CANCER)
• Ecological study design provide one way of avoiding these
difficulties and studying the effects of environmental
exposures and different health outcomes.
ECOLOGICAL STUDY:

23.  Frequently used in environmental epidemiology where it is
difficult to measure exposure at the individual level.
 Generally use pre-existing data, which have been collected for
other purposes and which can be available on large populations
• there are many sources of environmental data, from
environmental surveillance systems which can be used (air
pollution, drinking water quality, temperatures…)
 Can also be used for studying infectious diseases, especially in
surveillance, in order to detect signals which can be alerts.
 Also useful to evaluate the impact of intervention programs or
policies.
ECOLOGICAL STUDY DESING:

24.  To identify changes in the frequency of an
health event in space and/or time.
 To relate these changes with environmental
factors.
PRINCIPAL OF ECOLOGICAL
STUDY:

26. oA study in which researcher manipulates one
of the variables and tries to determine how
the manipulation influences other variables.
INTRODUCTION:

27. Randomized Control Trials
Field Trials
Community Trials
 TYPES OF EXPERIMENTAL
TRIALS:

28. Randomized Controlled Trials (RCT) is a study
in which a group of investigators studies two
interventions in a series of individuals who
receive them in a random order.
 RANOMIZED CONTROLLED TRIALS:

29. 1. The protocol
2. Selecting reference and experimental
populations
3. Randomization
4. Intervention
5. Follow up
6. Assessment
 BASIC STEP OF RANDOMIZED
CONTROLLED STUDY:

30. 1. Rationale
2. Aims and objectives, Research questions
3. Design of the study: selection of study and control
groups
4. Ethics: patient consent, adverse events
5. Documentation
6. Procedure
 THE PROTOCOL:

31. • Reference or target population - population to
which the findings of the trial, if found
successful, are expected to be applicable (eg.
drugs, vaccines, etc.)
• Experimental or study population - actual
population that participates in the
experimental study
 SELECTING REFERENCE AND
EXPERIMENTAL POPULATION:

32. • Must give informed consent.
• Should be representative of the population.
• Should be qualified or eligible for the trial.
 PARTICIPANTS MUST FULFILL
THE FOLLOWING CRITERIA:

33.  Heart of the control trial.
 Procedure: Participants are allocated into study and
control groups.
Eliminates bias and allows comparability .
Both groups should be alike with regards to certain
variables that might affect the outcome of the
experiment .
 Best done by using table of random numbers.
 RANDOMIZATION:

34. • Deliberate application or withdrawal or
reduction of a suspected causal factor.
• It creates an independent variable.
 INTERVENTION:

35. Interventions
Pharmaceutical (Therapeutic or Preventive)
Device
Procedure
Behavior modification
 TYPES OF INTERVENTION:

36. Implies examination of the experimental and
control group subjects
- at defined intervals of time,
- in a standard manner, with equal
intensity, under the same given circumstances
Attrition: Inevitable losses to follow up
 FOLLOW UP:

37. • Positive results
• Negative results
• Biases: Subject variation, Observer bias,
Evaluation bias
• Can be corrected by blinding
 ASSESSMENT:

39. Randomization is so important because
overall, it provides the strongest
evidence for causal inference.
 WHY RANDOMIZED ASSIGNMENT OF
INTERVENTION SO IMPORTANT?

40.  Clinical Trials
 - Diagnostic, Therapeutic, Prophylactic,
Devices, Procedures, Regimens, Protocols streptomycin for
treating TB
 Preventive Trials- pertusis vaccine
 Risk factor Trials- MRFIT
 Cessation Experiments- eg smoking
 Trial of aetiological agents- eg. Retrolental fibroplasia
 TYPES OF RANDOMIZATION:

41. • Excellent in determining cause-effect
relationships
• Great for evaluating new drugs and treatments
• Great for evaluating new programs
• Results can be easily analyzed
• Valid results since less variation and bias
 ADVANTAGES OF RANDOMIZATION:

42. Costly
Time consuming
Population that participates may not be
representative of the whole
Ethical dilemma – denying proper/best
treatment to all participants
 DISADVANTAGES OF
RANDOMIZATION:

43.  RANDOMIZED CONTROLLED TRIALS
LOOK LIKE:

44. • Involve people who are disease-free but
presumed to be at risk.
• Data collection – “in the field” – among non-
institutionalized people in the general
population.
• Used to evaluate interventions that reduce
exposure without measuring the occurrence
of health effects.
 FIELD TRIALS:

45. Hugh undertaking.
Major logistic considerations.
Major financial considerations.
Think of how much work is required to
randomize and allocate participants to various
treatment groups!
 LIMITATION OF FIELD TRIALS:

46. • Community Trials are usually carried out in
hospitals or clinics, and are usually directed at a
patient group with specific health conditions.
• However, randomized experiments are also
sometimes done in the community.
• In these types of studies, the major difference
from the RCT is that the randomization is done
on communities rather than individuals.
 COMMUNITY TRIALS: