Exogeny

• In an economic model, an exogenous change is one that comes from outside the model and is unexplained by the model.
• In econometrics, an exogenous variable is assumed to be fixed in repeated sampling, which means it is a :wikt:nonstochastic|nonstochastic variable. An implication of this assumption is that the error term in the econometric model is independent of the exogenous variable.
• In biology, an exogenous contrast agent in medical imaging for example, is a liquid injected into the patient intravenously that enhances visibility of a pathology, such as a tumor. An exogenous factor is any material that is present and active in an individual organism or living cell but that originated outside that organism, as opposed to an endogenous factor.
• *Exogenous factors in medicine include both pathogens and therapeutics.
• *DNA introduced to cells via transfection or viral transduction is an exogenous factor.
• *Carcinogens are exogenous factors.
• In geography, exogenous processes all take place outside the Earth and all the other planets. Weathering, erosion, transportation and sedimentation are the main exogenous processes.
• In attentional psychology, exogenous stimuli are external stimuli without conscious intention. An example of this is attention drawn to a flashing light in the of vision.
• In ludology, the study of games, an exogenous item is anything outside the game itself. Therefore, an item in a massively multiplayer online game would have exogenous value if people were buying it with real world money rather than in-game currency.
• In materials science, an exogenous property of a substance is derived from outside or external influences, such as a nano-doped material.
• In philosophy, the origins of existence of self, or the identity of self, emanating from, or sustaining, outside the natural or influenced realm, is exogenous.