[Qualitative and quantitative methods in biomedical research]

OBJECTIVE: To describe the main characteristics of the qualitative and quantitative research methods, to compare their differences, strengths and weaknesses, and to review complimentary assumptions. METHOD: Medline search and review of textbooks and selected articles. RESULTS: In order to understand the world where he lives, man organizes investigations along with philosophy, with religion and, in the last centuries, with science. The two principal paradigms of science adopt different research strategies. The quantitative paradigm, dominant in biomedical research, uses methods adopted from the physical sciences, epidemiology and statistics. These methods are used deductively, and aim to generate measures that are objective, reliable and generalizable. The qualitative paradigm uses methods that are common to anthropology, and are most conducted for discovery, identification, qualitative description, and explanation-generation. Each methodological approach has its own strengths and limitations, and it is the nature of the research question that will determine which approach is preferable. In many circumstances, the use of both approaches is necessary, as complimentary. CONCLUSIONS: Although qualitative methods are poorly known by many investigators, particularly by physicians, they are not new to medicine. In fact, medicine is based on qualitative methods, and both investigators and practitioners should use multiple methodologies in order to achieve better health and quality of life for their patients.