Quantitative and Qualitative Methods for Public Health
This course focuses on quantitative methods, which are designed to precisely estimate population parameters and measure the association between biologic, social, environmental, and behavioral factors and health conditions in order to define the determinants of health and disease and, ultimately, to understand causal pathways.
However, it is important to acknowledge the importance of qualitative methods which provide a means of understanding public health problems in greater depth by providing contextual information regarding a population's beliefs, opinions, norms, and behaviors. This type of information is difficult to capture using traditional quantitative methods, yet it can be vitally important for understanding the "why" for many health problems and also the "how" in terms of how to achieve improvements in health outcomes.
These two approaches might be thought of as the positivist and the constructivist approaches. In positivist research data are more easily quantified, but they are disconnected from the context in which they occur. For example, people of lower socioeconomic status are more likely to smoke tobacco, but the data collected does not indicate why. However, with a constructivist approach, the exposures that people are subjected to (or choose) are better understood in the context of their personal circumstances and the significance that people attribute to things in their environment.
Qualitative methods provide a means of understanding health problems and potential barriers and solutions in greater detail, and they provide an opportunity to understand the "how" and "why" and to identify overlooked issues and themes.
The table below, from the introductory course on fundamentals of public health, highlights some of the major differences between quantitative and qualitative research.
| Quantitative | Qualitative | |
|---|---|---|
| General Framework | Test hypotheses; data collection is rigid relying on structured methods, such as questionnaires, surveys, record reviews | Explore phenomena using more flexible methods that categorize responses to semi-structured methods such as in-depth interviews, focus groups, and participant observation |
| Analytic Objectives | Describe populations and to quantify exposure-outcome associations | Describe and explain variations and relationships |
| Question Format | Closed-ended | Open-ended |
| Data Format | Numeric or categorical | Textual (based on audiotapes, videotapes, and field notes) |
| Flexibility in Study Design | Study design is stable throughout a study. Participant responses do not influence or determine how and which questions researchers ask next. | The study design is more flexible. Participant responses affect how and which questions researchers ask next. Questions can be adjusted according to what is learned |