A dose-response curve is a graphic representation of the number or fraction of survivors in a living population as a function of the dose of a harmful or lethal agent to which the population has been exposed. It can be used as a more elaborate means to represent the lethality of a physical agent or toxicity of a poison than the familiar LD

, the dose that would cause 50% mortality in the affected population. The affected population can be humans, in which case the harmful agent would be not only a directly ingested poison, radiation or a carcinogen, etc. but also a toxin produced by a food-borne or an infectious microbe.