Natural Experiment

A natural experiment is an empirical study in which the experimental conditions (i.e., which units receive which treatment) are determined by nature or by other factors out of the control of the experimenters and yet the treatment assignment process is arguably exogenous. Thus, natural experiments are observational studies and are not controlled in the traditional sense of a randomized experiment. Natural experiments are most useful when there has been a clearly defined and large change in the treatment (or exposure) to a clearly defined subpopulation (and no change to a comparable subpopulation), so that changes in responses may be plausibly attributed to the change in treatments (or exposure).

Natural experiments are considered for study designs whenever controlled experimentation is difficult, such as in many problems in epidemiology and economics.

Read more about Natural Experiment:  History

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... Sir David Attenborough (born 1926), English natural history presenter and anthropologist ... He is also known for the Cavendish experiment, his measurement of the Earth's density, and early research into electricity ... Charles Darwin (1809–1882), founder of the theory of evolution by natural selection, once described himself as being generally agnostic, though he was a member of the Anglican ...
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