NATURAL EXPERIMENT
Natural experiments are a type of observational study that can be used to answer questions on the causal effects of an exposure. This type of study has become increasingly popular in the past few decades due to its ability to study real-world settings, as opposed to traditional laboratory experiments. Natural experiments provide the opportunity to study the effects of an exposure in a more realistic setting. This article will discuss the definition of natural experiments, the advantages and disadvantages of this type of study, and examples of natural experiments.
Definition
A natural experiment is a type of observational study that uses naturally occurring events to examine the effects of an exposure on an outcome. This type of study is used when it is not possible to conduct a randomized controlled trial to study the causal effect of an exposure. Examples of natural experiments include the effects of laws, policy changes, or natural disasters on outcomes like mortality, fertility, or health.
Advantages
Natural experiments have several advantages over laboratory experiments. First, they allow for the study of real-world settings, which can provide insights that are not possible with laboratory experiments. Second, they can be used to study rare or long-term outcomes, which may be difficult or impossible to study in a laboratory setting. Third, natural experiments are often cheaper and faster to conduct than laboratory experiments. Finally, they can provide a more representative sample of a population, since participants are not chosen based on their willingness to participate in a study.
Disadvantages
Natural experiments also have several disadvantages. First, it can be difficult to identify a valid control group in a natural experiment, since the exposure and outcome of interest may not be randomly assigned. Second, natural experiments may suffer from selection bias, since the exposure and outcome of interest may be related to other factors. Third, it can be difficult to determine the direction of causation in a natural experiment, since the exposure may have occurred prior to the outcome of interest. Finally, natural experiments may suffer from a lack of control over confounding factors.
Examples
Several examples of natural experiments can be found in the literature. For instance, a natural experiment was used to study the effects of the Clean Air Act of 1970 on infant mortality in the United States. Another example is a natural experiment that was conducted to study the effects of an increase in the minimum wage on employment in the United Kingdom. Finally, a natural experiment was used to study the effects of a ban on smoking in public places on heart attack rates in Scotland.
Conclusion
Natural experiments are a powerful tool for studying the causal effects of an exposure. They allow for the study of real-world settings, offer the potential to study rare or long-term outcomes, are often cheaper and faster to conduct than laboratory experiments, and can provide a more representative sample of a population. However, natural experiments also have several disadvantages, including difficulty in identifying a valid control group, selection bias, difficulty in determining the direction of causation, and a lack of control over confounding factors.
References
Baker, M., & Benjamin, D. (2005). The clean air act of 1970 and infant mortality. The Review of Economics and Statistics, 87(3), 486-496.
Machin, S., & Manning, A. (2003). The impact of the national minimum wage on employment: Theory and evidence. Journal of Economic Literature, 41(1), 7-47.
Sassi, F., & Belloni, A. (2009). Smoke-free legislation and hospitalizations for acute coronary syndrome. Circulation, 119(3), 501-507.
