in fact, epidemiology is often described as the basic science of public health and for good reason. first, epidemiology is a quantitative discipline that relies on a working knowledge of probability, statistics, and sound research methods. second, epidemiology is methods of causal reasoning based on developing and testing hypotheses grounded in such scientific fields as biology, behavioral sciences, physics, and ergonomics to explain health-related behavioral, states, and events. However, epidemiology is not just a research activity but an integral component of public health, providing the foundation for directing practical and appropriate public health action based on this science and causal reasoning.