1. Data Collection Methods
Amr Albanna, MD, MSc

2. Objectives
1. Determine the information required for your
study.
2. Understand the different types of data.
3. Learn about different sources of data.
4. Know the criteria to select the data collection
method.
5. Learn how to enter the data in an analyzable
format.

3. Required Information
• Population
– Factors that define the population (generalizability).
• Exposure
– Definition.
• Outcome
– Definition.
• Factors that could influence the association
between exposure and outcome (confounding
factors).

4. Types of Data
• Qualitative Data
• Quantitative Data

5. Qualitative Data
• Tend to be open-ended and have less structured
protocols.
• Rely more heavily on interactive interviews.
• Small number of subjects.
• Findings are not generalizable to any specific
population.

7. Qualitative Data
• Utility:
– Useful to understand the processes behind
observed results.
– Help in generating hypothesis to design
quantitative research.

8. • Rely on random sampling.
• Structured data collection methods.
• Produce results that are easy to summarize,
compare, and generalize.
Quantitative Data

9. Example: Student Evaluation of a
CourseQuantitative
Qualitative

10. Sources of data
Primary
• Clinical observations
• Questionnaires and
interviews
Secondary
• Reportable diseases,
registries
• Administrative
databases (hospital
discharges, medication
prescriptions)
• Hospital charts
• Vital statistics

11. Personal interview
• Face-to-face  more response
• Telephone  less response
• Better for complex, semi-structured questions
• Errors:
– Social desirability bias
– Recall error

12. Self-administered questionnaire
• Paper, computer
• Better for sensitive data
• Cheaper (main advantage)
• Low response rate
• Errors
– Misunderstanding
– Recall error

13. Use of Records
• Medical records
• Electronic databases
• Advantages:
– Less recall errors (information has been reported prospectively)
– Low cost
• Disadvantages:
– May not cover all required information
– Inconsistent case definition between reporters
– Missing data
– Reporting errors

14. Other Data Collection Methods
• Observation:
– E.g., diet
– Use of a medical device
• Proxy respondents
– E.g., For dead, incompetent or disabled subjects
• Diaries
– For frequent behaviors (e.g. diet, exercise)
• Physical, chemical measures
– Individual
– Environmental

15. Criteria to Select the Method
• Appropriate to purpose
• Feasible
• Respondent burden
• Cost
• Acceptability
• Simplicity
• Meaningful
• Reliability
• Validity
• Responsiveness
(sensitivity to change)

16. • Validity (accuracy):
– The degree to which a tool measures what it
claims to measure.
• Reliability (consistency):
– The tool of measurement produces similar results
under consistent conditions.
Criteria to Select the Method

18. Data Collection Sheet
Data extraction form

19. Data Entry (Analyzable Format)
Variable-1 Variable-2 Variable-3
Unit-1
Unit-2
Unit-3
Unit-4

20. Type of Variable
• Continuous
e.g. Age, weight, blood pressure….
• Categorical (discrete)
– Dichotomous (binary)
– Polychotomous (multi-category)
• Nominal
• Ordinal

21. Unit of Analysis
• Individual data
– Patients
– Physician
• Cluster (group) data
– Meta-analysis
– Ecologic study

22. Individual Data

23. Data Extraction/Entry

24. Questions