ABSTRACT
Epidemiology is the study of the distribution and determinants of the various forms of disease in human populations. Its focus is not on the individual case of ill health, but rather on groups of people, both healthy and diseased. When investigating a particular disease (such as lung cancer), epidemiologists try to relate its occurrence and distribution to a variety of factors associated with most victims of that condition (such as smoking behaviour) in order to discover its probable aetiology. The factors most commonly examined are the age, sex, marital status, occupation, socio-economic position, diet, environment (both natural and manmade) and behaviour of the victims. Their aim is to uncover a causal link between one or more of these factors and the development of the disease.
