data collection methods rss6 2014
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Data Collection Methods
Amr Albanna, MD, MSc
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.
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).
Types of Data
• Qualitative Data
• Quantitative Data
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.
Qualitative Data
• Utility:
– Useful to understand the processes behind observed results.
– Help in generating hypothesis to design quantitative research.
• Rely on random sampling.
• Structured data collection methods.
• Produce results that are easy to summarize, compare, and generalize.
Quantitative Data
Example: Student Evaluation of a Course Quantitative
Qualitative
Sources of data
Primary
• Clinical observations
• Questionnaires and interviews
Secondary
• Reportable diseases, registries
• Administrative databases (hospital discharges, medication prescriptions)
• Hospital charts
• Vital statistics
Personal interview
• Face-to-face more response
• Telephone less response
• Better for complex, semi-structured questions
• Errors: – Social desirability bias
– Recall error
Self-administered questionnaire
• Paper, computer
• Better for sensitive data
• Cheaper (main advantage)
• Low response rate
• Errors – Misunderstanding
– Recall error
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
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
Criteria to Select the Method
• Appropriate to purpose
• Feasible
• Respondent burden
• Cost
• Acceptability
• Simplicity
• Meaningful
• Reliability
• Validity
• Responsiveness (sensitivity to change)
• 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
Data Collection Sheet
Data extraction form
Data Entry (Analyzable Format)
Variable-1 Variable-2 Variable-3
Unit-1
Unit-2
Unit-3
Unit-4
Type of Variable
• Continuous
e.g. Age, weight, blood pressure….
• Categorical (discrete)
– Dichotomous (binary)
– Polychotomous (multi-category)
• Nominal
• Ordinal
Unit of Analysis
• Individual data
– Patients
– Physician
• Cluster (group) data
– Meta-analysis
– Ecologic study
Individual Data
Data Extraction/Entry
Questions
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