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