Epidemiology is the study of the distribution and spread of disease or illness at the population level. Epidemiologists make use of techniques and approaches from numerous fields. Statistical and mathematical models drawn from biostatistics may be used to model or predict disease rates, while social science approaches such as interviewing and survey research might be used to elucidate information on social risk factors for disease. Epidemiology is considered one of the foundational methods employed in the practice of public health.
Drawing distinctions between health services research, epidemiology, and clinical research can be challenging, as these all generally share the same biostatistical foundation and differ only in approach and subject matter. Health services research focuses on the health care system, epidemiology focuses on population-level distributions of disease, and clinical research focuses on specific aspects of clinical care. Questions regarding all three can be placed under this tag, as CrossValidated does not have an HSR or clinical research tag.
Clinical trials - specifically designed trials for new drugs or interventions with strict regulatory guidance and statistical methods - are separate from these fields, and should be put under the