demos, meaning people, and logos, meaning the study of. In other words,the word epidemiology has its roots in the study of what befalls a population. Many definitions have been proposed, but the following definnition captures the underlying principles and public health spirit of epidemiology :
......Epidemiology is the study of the distribution and determinants of health-related states or events in specified population, and the application of this study to the control of health problems.
Key terms in this definition reflest some of the important principles of epidemiology.
....Study....
.....Epidemiology is a scientific discipline with sound methods of scientific inquiry at its foundation. Epidemiology is data-driven and relies on a systematic and unbiased approach to the collection, analysis, and interpretation of data. Basic epidemiologic methods tend to rely on careful observation and use of vaild comparison groups to assess whether what was observed, such as the number of cases of disease in a particular area during a particular time period or the frequency of an exposure among persons with disease, differs from what might be expected. However, epidemiology also draws on methods from other scientific fields, including biostatistics and informatics, with biologic, economic, social, and behavioral sciences.
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In fact, epidemolology 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, statis, and sound research method .Second epidemiology is a method of causal reasoning based on developingand tesing hypotheses grounded in such sciendtific fields as biology behaviors, sciences, physics , and ergonomics to explain health-related behaviors, 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