Editing Experiment (section)

==Overview==
In the [[scientific method]], an experiment is an [[Empirical research|empirical]] procedure that arbitrates competing [[scientific models|models]] or [[hypotheses]].<ref>{{cite book|last1=Cooperstock|first1=Fred I.|title=General Relativistic Dynamics: Extending Einstein's Legacy Throughout the Universe|date=2009|publisher=World Scientific|location=Singapore|isbn=978-981-4271-16-5|page=12|edition= Online-Ausg.}}</ref><ref name=Griffith>{{cite book|last1=Griffith|first1=W. Thomas|title=The physics of everyday phenomena : a conceptual introduction to physics|date=2001|publisher=McGraw-Hill|location=Boston|isbn=0-07-232837-1|pages=[https://archive.org/details/physicsofeveryda00grif_0/page/3 3–4]|edition=3rd|url=https://archive.org/details/physicsofeveryda00grif_0/page/3}}</ref> Researchers also use experimentation to test existing [[Scientific theory|theories]] or new hypotheses to support or disprove them.<ref name=Griffith/><ref name=Wilczek>{{cite book|last1=Wilczek|first1=Frank|last2=Devine|first2=Betsy|title=Fantastic realities : 49 mind journeys and a trip to Stockholm|date=2006|publisher=World Scientific|location=New Jersey|isbn=978-981-256-649-2|pages=61–62}}</ref>

An experiment usually tests a [[hypothesis]], which is an expectation about how a particular process or phenomenon works. However, an experiment may also aim to answer a "what-if" question, without a specific expectation about what the experiment reveals, or to confirm prior results. If an experiment is carefully conducted, the results usually either support or disprove the hypothesis. According to some [[philosophy of science|philosophies of science]], an experiment can never "prove" a hypothesis, it can only add support. On the other hand, an experiment that provides a [[counterexample]] can disprove a theory or hypothesis, but a theory can always be salvaged by appropriate [[ad hoc]] modifications at the expense of simplicity.{{cn|date=April 2025}}

An experiment must also control the possible [[confounding|confounding factors]]—any factors that would mar the accuracy or repeatability of the experiment or the ability to interpret the results. Confounding is commonly eliminated through [[scientific control]]s and/or, in [[randomized experiment]]s, through [[random assignment]].{{cn|date=April 2025}}

In [[engineering]] and the [[Outline of physical science|physical sciences]], experiments are a primary component of the scientific method. They are used to test theories and hypotheses about how physical processes work under particular conditions (e.g., whether a particular engineering process can produce a desired chemical compound). Typically, experiments in these fields focus on [[Replication (statistics)|replication]] of identical procedures in hopes of producing identical results in each replication. Random assignment is uncommon.

In [[medicine]] and the [[social sciences]], the prevalence of experimental research varies widely across disciplines. When used, however, experiments typically follow the form of the [[clinical trial]], where experimental units (usually individual human beings) are randomly assigned to a treatment or control condition where one or more outcomes are assessed.<ref>{{cite journal|last1=Holland|first1=Paul W.|title=Statistics and Causal Inference|journal=Journal of the American Statistical Association|date=December 1986|volume=81|issue=396|pages=945–960|doi=10.2307/2289064|jstor=2289064}}</ref> In contrast to norms in the physical sciences, the focus is typically on the [[average treatment effect]] (the difference in outcomes between the treatment and control groups) or another [[test statistic]] produced by the experiment.<ref>{{cite book|editor-last1=Druckman|editor1-link=James N. Druckman|editor3-link=James Kuklinski|editor-first1=James N.|editor2-link=Donald Green|editor-last2=Green|editor-first2=Donald P.|editor-last3=Kuklinski|editor-first3=James H.|editor-last4=Lupia|editor4-link=Arthur Lupia|editor-first4=Arthur|title=Cambridge handbook of experimental political science|date=2011|publisher=Cambridge University Press|location=Cambridge|isbn=978-0521174558}}</ref> A single study typically does not involve replications of the experiment, but separate studies may be aggregated through [[systematic review]] and [[meta-analysis]].{{cn|date=April 2025}}

There are various differences in experimental practice in each of the [[branches of science]]. For example, [[agriculture|agricultural]] research frequently uses randomized experiments (e.g., to test the comparative effectiveness of different fertilizers), while [[experimental economics]] often involves experimental tests of theorized human behaviors without relying on random assignment of individuals to treatment and control conditions.{{cn|date=April 2025}}