1. The document discusses various research designs including descriptive designs like case reports, case series, and cross-sectional studies as well as analytical designs like case-control and cohort studies. 2. Key aspects of different research designs are explained, including their merits and limitations. For example, case reports are useful for rare diseases but cannot assess statistical associations, while cohort studies directly measure risk but are time-consuming. 3. Randomized controlled trials are covered, outlining basic steps like drawing protocols, randomization, and intervention/follow-up. Randomization techniques like simple, block, and stratified methods are also summarized.

1. Research Design
D.A. Asir John Samuel, BSc (Psy),
MPT (Neuro Paed), MAc, DYScEd,
C/BLS, FAGE

2. Meaning of research design
• The arrangement of conditions for
collection and analysis of data in a
manner that aims to combine
relevance to the research purpose
with economy in procedure
Dr. Asir John Samuel (PT), Lecturer, ACP 2

3. Need for research design
• Smooth sailing of various research operations
• Yielding maximal information
• Minimal expenditure of effort, time & money
• Plan for house
• Advance planning of methods to be adopted
for collecting relevant data and techniques to
be used in analysis
Dr. Asir John Samuel (PT), Lecturer, ACP 3

4. Need for research design
• Efficient and appropriate design must be
prepared before starting research operation
OR futile
• Organize ideas in a form
• Possible to look for flaws & inadequacies
• Need for providing comprehensive review
Dr. Asir John Samuel (PT), Lecturer, ACP 4

5. Features of good research design
• Flexible
• Appropriate
• Efficient
• Economical
• Minimises bias
• Maximises the reliability of collected data and
analysed
Dr. Asir John Samuel (PT), Lecturer, ACP 5

6. Features of good research design
• A research design should consider,
- Means of obtaining information
- Objective of the problem to be studied
- Nature of the problem to be studied
- Availability of time and money
• Emphasis on discovery of ideas and insights
• Hypothesis if casual relationship b/w variables
Dr. Asir John Samuel (PT), Lecturer, ACP 6

7. Different research designs
Study designs
Observational Experimental
Descriptive Analytical RCT Non-RCT
Cross-
Case control
Case report Case series sectional Cohort
study
study
Dr. Asir John Samuel (PT), Lecturer, ACP 7

8. Case report
• Studies describing the characteristics of a
single patient
Dr. Asir John Samuel (PT), Lecturer, ACP 8

9. Case report-merits
• Record unusual medical occurrences and can
give the first clues in identification of a new
disease or adverse effects of an exposure
• Only means of surveillance for rare clinical
events
• Serve to elucidate the mechanism of disease
and treatment
Dr. Asir John Samuel (PT), Lecturer, ACP 9

10. Case report-Demerits
• Cannot be used to test for the presence of
valid statistical association because it is based
on the experience of one person
Dr. Asir John Samuel (PT), Lecturer, ACP 10

11. Case series
• Studies describing the characteristics of a
group of patients with similar diagnosis
• Collection of 5 & more cases
Dr. Asir John Samuel (PT), Lecturer, ACP 11

12. Case series-merits
• Helps in formulating a useful hypothesis
regarding risk factors of disease or identifying
a new disease or outcome of new treatment
• Informative for very rare disease with few
established risk factors
• May suggest the emergence of a new disease
or epidemic
Dr. Asir John Samuel (PT), Lecturer, ACP 12

13. Case series-Demerits
Cannot be used to test for the presence of valid
statistical association due to absence of a
comparison group
Dr. Asir John Samuel (PT), Lecturer, ACP 13

14. Cross-sectional studies
• Single examination of a cross section of
population at one point of time
• Helps to generate a hypothesis
• Used to investigate non fatal diseases
• Both exposure and outcome (disease) are
determined simultaneously for each subject
• Provide information about the frequencey or
characteristic of disease
Dr. Asir John Samuel (PT), Lecturer, ACP 14

15. Cross-sectional studies-Merits
• Provide information about the frequency of an
attribute and potential risk factors
• Helps to generate a hypothesis
• Can give a good picture about the health care
needs of the population at the point of time
• Can be used to investigate multiple exposure
and multiple outcome
• Suitable for chronic cases
Dr. Asir John Samuel (PT), Lecturer, ACP 15

16. Cross-sectional studies-Demerits
• Difficult to establish the time of sequence of
events
• They are not suitable to investigate rare
diseases, rare exposure or disease of short
duration
• Being based on prevalent rather than incident
cases
• Limited value to investigate etiological
relationship
Dr. Asir John Samuel (PT), Lecturer, ACP 16

17. Case control study
• Type of analytical study
• By observation and analysis
• Retrospective evaluation to determine who
was exposed and who was not exposed –
retrospective study
Dr. Asir John Samuel (PT), Lecturer, ACP 17

18. Case control study
• To examine the possible relation of an
exposure to certain disease
- Identify the individual having the disease –
case
- Individual don’t have the disease –
comparison purpose
Dr. Asir John Samuel (PT), Lecturer, ACP 18

19. Case control study
Factor (s)
Present individuals with disease
TIME
Direction of enquiry
Absent individuals w/o disease
Dr. Asir John Samuel (PT), Lecturer, ACP 19

20. Case control study
4 basic steps in conducting a case control study,
1. Selection of cases and controls
2. Matching
3. Measurement of exposure
4. Analysis and interpretation
Dr. Asir John Samuel (PT), Lecturer, ACP 20

21. Case control study – Merits
• Quick, less expensive
• Well suited for disease with long latent period
• Optimal for evaluation of rare diseases
• Can study etiological factors for a single
disease
• Requires small sample than a cohort study
• No attrition (drop outs) problem
• Ethical problems are minimal, no risk to
subjects
Dr. Asir John Samuel (PT), Lecturer, ACP 21

22. Case control study- Demerits
• More prone to bias
• Selection of appropriate control group may be
difficult
• Inefficient for evaluation of rare exposure
• Cannot directly measure incidence, can only
estimate relative risk
Dr. Asir John Samuel (PT), Lecturer, ACP 22

23. Cohort study
• Forward looking study
• Prospective study
• Incidence study
• Longitudinal study
• There is regular follow up over a period of
time
Dr. Asir John Samuel (PT), Lecturer, ACP 23

24. Cohort study
Factor (s)
Individuals exposed Present
TIME
Direction of enquiry
individuals unexposed Absent
Dr. Asir John Samuel (PT), Lecturer, ACP 24

25. Cohort study
• Proceeds from cause to effect
• Exposure has occurred when the study is
initiated, but the disease has not occurred
Dr. Asir John Samuel (PT), Lecturer, ACP 25

26. Cohort
• A group of people who share a common
characteristic or experience within a defined
time period
• Cohort must be free from disease under study
• Both groups (study cohort & control cohort)
should be equally susceptible for the disease
under study
• Should be comparable in all possible variables
Dr. Asir John Samuel (PT), Lecturer, ACP 26

27. Cohort study
• Elements of a cohort study,
1. Selection of study subjects
2. Obtaining data on exposure
3. Selection of comparison group
4. Follow-up
5. Analysis
Dr. Asir John Samuel (PT), Lecturer, ACP 27

28. Cohort study - Merits
• Incidence can be calculated
• Examines multiple effects of a single exposure
• Provides direct estimate of relative risk
• Minimizes bias
• Dose-response ratios can be calculated
• Elucidates temporal relationship b/w exposure
& disease Dr. Asir John Samuel (PT), Lecturer, ACP 28

29. Cohort study - Demerits
• Inefficient for rare diseases
• Expensive and time consuming
• Involves large sample size
• Alters people behaviour
• Changes in standard methods or diagnostic
criteria of disease over prolonged follow-up
Dr. Asir John Samuel (PT), Lecturer, ACP 29

30. RCT
• Basic steps in conducting a RCT,
1. Drawing up a protocol
2. Selecting reference & exp. Group
3. Randomization
4. Manipulation or intervention
5. Follow-up
6. Assessment of outcome
Dr. Asir John Samuel (PT), Lecturer, ACP 30

31. Select
suitable
population
Select
suitable
sample
Exclusions
Randomize
Experimental
Control group
group
Intervention
& follow-up
Dr. Asir John Samuel (PT), Lecturer, ACP 31

32. SACKETT LEVEL OF EVIDENCE
Dr. Asir John Samuel (PT), Lecturer, ACP 32

33. Randomization
• Simple randomization
• Block randomization
• Stratified randomization
• Unequal randomization
Dr. Asir John Samuel (PT), Lecturer, ACP 33