Assertion: natural experiment | /r/HasProperty | employed as study designs
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text: Natural experiments are employed as study designs when controlled experimentation is extremely difficult to implement or unethical, such as in several research areas addressed by epidemiology (like evaluating the health impact of varying degrees of exposure to ionizing radiation in people living near Hiroshima at the time of the atomic blast) and economics (like estimating the economic return on amount of schooling in US adults).