about research design

1. Dr Azmawati Mohammed Nawi
OVERVIEW OF RESEARCH
DESIGN

2. Which one?
Quantitative
or
Qualitative

3. Definitions of Qualitative
and Quantitative
Research
Quantitative
Research
A type of medical
research in
which the researcher
decides
what to study, asks
specific,
narrow questions,
collects
numeric (numbered)
data
from participants,
Qualitative Research
A type of medical
research in
which the researcher
relies on
the views of participants,
asks
broad, general
questions,
collects data consisting
largely of
words (or text) from
participants,

4. Characteristics of Quantitative and
Qualitative Research in the Process of
Research

5. Ways in Which Quantitative and
Qualitative Research are Similar
 They both follow the steps in the process of
research
 Format for reporting the research problem is
the same
 Both have data collection steps

10. How Do You Choose Whether to Use
the Quantitative or Qualitative
Approach?
 Match the approach to the problem
 Fit the approach to your audience
 Relate the approach to your
experiences

11. Classification of Study
Design
 Whether the subject were merely observed or
whether some intervention was performed
 Can be divided into two categories:
– Observational Studies
• one of more group of patients are observed
and characteristics about the patients
are recorded for analysis
– Experimental Studies
• an investigator-controlled maneuver -and
interest lies
in the effect the intervention has on study
subject

12. Question need to be
answer…
 ?distribution of blindness - descriptive
 ?correlation between import of fruits and visual
acuity among the population - ecological
correlation
 ?prevalence of blindness, cataract or poor vision -
cross-sectional/survey
 ?association between vit A def. and blindness -
case-control
 ?incidence and relative risk of radiation
cataract among radiographers- cohort
 ?therapy/preventive methods useful or effective ,
daily vit A supplementation to prevent
xeropthalmia - intervention

14. CASE
REPORT/SERIES
 Used as early means to identify the beginning or
presence of an epidemic (surveillance data).
 Formulation a new hypothesis then
 Use analytic studies to identify possible causal
factors.

15. CORRELATIONAL/ECOLOGICAL
STUDIES
 Involves collection of information about one or
more characteristics of a clearly defined
population and relating to the number of
individuals that form the population
 The population may be defined according to
geographical, geopolitical or time criteria

16. CROSS SECTIONAL
STUDY
 Examines the relationship between diseases and
other variable of interest as they exist in a defined
population at one particular time
 Disease exposure and status are concurrently
evaluated among individuals in a population
 Conducted at one period of time or at one time
 Provide information regarding the prevalence of a
disease
 Normally tries to find association and not testing
the hypothesis

18. DISEASE
PRESENT ABSENT
+ A B
- C D
-----------------------------------
A + C B + D
CROSS-SECTIONAL STUDY
EXPOSE

19. CROSS-SECTIONAL SURVEY
 RESEARCH QUESTIONS
- What is the nature / magnitude of the problem?
- Who is affected?
- How do the affected people behave?
- What do they know, believe, think about the
problem?
We know very little about the problems and its
possible causes

20. CROSS-SECTIONAL SURVEY
MAY BE REPEATED - to
measure changes over time
LARGE SURVEY - limited
variables
 SMALL SURVEY - unlimited

21. CROSS-SECTIONAL
COMPARATIVE STUDY
 ANALYTICAL STUDY
 attempts to establish causes or risk factors for
certain problems.
 ex : obesity and IGT
 level of cholesterol and CHD
 betel leaves and NIDDM
 milk consumption and IDDM

22. CROSS-SECTIONAL STUDY
ADVANTAGES
 cheap and fast
 hypothesis
generating
 able to generalise
 prevalence -
planning,
disease load, high risk
population.
 baseline for cohort
DISADVANTAGES
 show association
only
 survivors problems
 not for rare diseases,
remission etc.
 possible biases -
selection, misclass’n,

24. CASE
CONTROL
 Is an observational study in which diseased and
non diseased (or affected and no affected)
subjects are identified after the fact and then
compared regarding specific characteristics to
determine possible association or risk for disease
in question

26. CASE SELECTION
 Determine clear and reproducible
definitions of the health problems to be
studied (avoid misclassification bias)
 source of cases
All persons with the disease seen in
particular facility(ies) in a specified period
of time.
All persons with the disease found in
general population.
Incident cases (newly diagnosed cases)

27. CHOICE OF CONTROLS
 Controls should ideally be selected from
the same population gave rise to cases
 Similar to cases in regard to past potential
exposure
 Free from study disease
 If controls are patient with other diseases
then only diseases that are not known to
have relationship with factors under study
will be selected.

28. MATCHING
 to take account for potentially confounding
variables
 type of matching :
• Frequency matching : selection of controls
with the same proportionate distribution of
the particular variable as the cases. (eg. age
and sex)
•Individual matching : pairing the controls
with the cases on some common variables
such as age, sex and ethnic group.
• Matched variables cannot be evaluated

29. ASSESSMENT OF EXPOSURE
 Exposure should be assessed by the same
method for both cases and controls
 blinding
 methods of assessment :
• available records - hospital, vital, employment
•interview
•self-administered questionnaire
•direct measurement
• Comparability of the accuracy and completeness of data

30. MATCHED PAIR C-C STUDY
CASES
Exposed Not exposed
Exposed
Not exposed
a b
(both pairs exposed) ( pairs of controls exposed)
c d
(pairs of cases exposed) (both pairs not exposed)
C
O
N
T
R
O
L

32. COHORT
STUDY
 One or more individual groups are defined based
on whether exist or not the exposure to a disease
factor
 During the exposure status is defined, all subjects
are free from the studied disease
 Cohort study is normally prospective (i.e.
exposure factor and subsequently the health
effects are observed after the beginning of the
study)
 Other name for this type of study:longitudinal
study

35. SELECTION OF COHORTS
 SOURCES :
- geographically defined groups
- special resource groups -doctors, nurses,
factory workers etc.
- special exposure group - expose to
radioactive, asbestos, benzene, haze
 COMPARISON GROUPS :
- similar in all respects except exposure

36. ASSESSMENT OF EXPOSURE
AND OUTCOME
INFORMATION ON EXPOSURE:
 records, cohort members, medical examination
and measures of the environment
INFORMATION ON OUTCOME
 periodic reexamination
 surveillance of deaths, hospitalization, clinic
visits

40. Experimental
Studies
 The hallmark of the experimental study is that the
allocation
or assignment of individuals is under control of
investigator and thus can be randomized.
 The key is that the investigator controls the
assignment of the exposure or of the treatment
but otherwise symmetry of potential unknown
confounders is maintained through
randomization.
 Properly executed experimental studies provide
the
strongest empirical evidence.
 The randomization also provides a better
foundation for statistical procedures than do

41. Randomized Controlled Clinical Trial
(RCT)
 A prospective, analytical, experimental study
using primary data generated in the clinical
environment.
 Individuals similar at the beginning are randomly
allocated to two or more treatment groups and
the outcomes the groups are compared after
sufficient follow-up time.
 The strongest evidence of the clinical efficacy of
preventive and therapeutic procedures in the
clinical setting.

42. Randomized Cross-Over Clinical
Trial
 A prospective, analytical, experimental study
using primary data generated in the clinical
environment.
 Individuals with a chronic condition are randomly
allocated to one of two treatment groups, and,
after a sufficient treatment period and often a
washout period, are switched to the other
treatment for the same period.
 This design is susceptible to bias if carry over
effects from the first treatment occur.

43. Randomized Controlled Laboratory
Study
 A prospective, analytical, experimental study
using primary data generated in the laboratory
environment.
 Laboratory studies are very powerful tools for
doing basic research because all extraneous
factors other than those of interest can be
controlled or accounted for (e.g., age,
gender,genetics, nutrition, environment,
comorbidity, strain of infectious agent).

44. EXPRIMENTAL STUDY
STUDY POPULATION
SELECTION
ELIGIBLE
PARTICIPANTS NOT ELIGIBLE
PARTICIPANTS NON-PARTICIPANTS
RANDOMISATION
TREATMENT CONTROL

45. SELECTION OF SUBJECTS
 Number, sources
 Inclusion criteria : age range, sex, weight,
diagnostic criteria, informed consent,
cooperation
 Exclusion: lack of inclusion criteria,
pregnancy or lactation, drug allergy, disease
severity, other disorders, requirement of other
drugs, unresponsive cases, mental status.

46. RANDOMISATION
 Method for inducing comparability between
groups
 Ensures that characteristics known or
unknown did not influence the treatment
assigned
 Treatment given to the patient / next patient to
enter the trial is determined purely by chance,
not by any characteristics of the patient

47. RANDOMISATION
 Allows the computation of the probability that
the groups differ for both known and unknown
characteristics.
 Does not guarantee perfect comparability
 Better than any known procedure
 Each patient enter the trial has an equal
chance of receiving which ever therapy

48. COMPARISON GROUP
 To allow the evaluation of the outcomes of
interest in a comparable group of patients who
received a standard or best available relevant
alternative treatment
 The effect of treatment are compared to the
effects of a control treatment

49. COMPARABILITY
 The patients should not differ in any
characteristics, known or unknown, relevant to
the outcomes of interest other than the treatment
employed.

50. ADMINISTRATION OF STUDY
 Institutional review – ethical committee
 Informed consent
 Receipt, distribution and storage of
investigational supplies
 Instructions to recorders
 Instructions to subjects
 Adverse reaction reporting
 Monitoring
 Reporting results

51. PROCEDURE
 Assignment of subjects to treatments
 Interview and examinations
 Methods of assessment
 Lab. Studies
 Treatment schedules: number of units per
visit, rules fo changing dosage, compliance
checks
 Adverse reactions: definition and grading,
inquiry, management.
 Drops out: definition, handling and recording,
terminating and extending study

52. BLINDING
 Single blind : either the patient or the physician
knows the treatment which has been assigned
 Double blind: neither the patients nor the
physician are aware of the treatment assigned
 Triple blind: even the statistician not aware of the
assignment.

53. FOLLOW-UP SCHEDULE
 The schedule of visits
 The duration of follow-up
 Measurement and procedures to be conducted at
each visits
 In multi-centre trial, the methodology of all
measurements and procedures should be
specified thoroughly.

55. EXPRIMENTAL STUDY
ADVANTAGES
 the best design to
determine causal
association and
evaluate program
performance
DISADVANTAGES
 expose to selection,
attrition, compliance
and contamination
biases.
 ethical implications

56. Quasi
experiment
 Quasi-experiment is a research design having
some but not all of the characteristics of a true
experiment.
 The element most frequently missing is random
assignment of subjects to the control and
experimental conditions.
 Examples of quasi-experiment research design
are the natural experiment (where nature has
assigned subjects to the two conditions) or trend
analysis.

57. Discussio
n

59. THANK YOU