Hypothesis

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{{short description|Proposed explanation for an observation, phenomenon, or scientific problem}}
{{other uses|Hypothesis (disambiguation)|Hypothetical (disambiguation)}}
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[[File:Cellarius Harmonia Macrocosmica - Hypothesis Ptolemaica.jpg|thumb|right|350px|The hypothesis of [[Andreas Cellarius]], showing the planetary motions in eccentric and epicyclical [[orbit]]s.]]

A '''hypothesis''' ({{plural form}}: '''hypotheses''') is a proposed [[explanation]] for a [[phenomenon]]. For a hypothesis to be a scientific hypothesis, the [[scientific method]] requires that one can [[testable|test]] it. [[Scientist]]s generally base scientific hypotheses on previous [[observation]]s that cannot satisfactorily be explained with the available scientific theories. Even though the words "hypothesis" and "[[theory]]" are often used interchangeably, a scientific hypothesis is not the same as a [[scientific theory]]. A [[working hypothesis]] is a provisionally accepted hypothesis proposed for further [[research]]<ref name="HilbornMangel1997"/> in a process beginning with an educated guess or thought.<ref name=Feynman /> 

A different meaning of the term ''hypothesis'' is used in [[formal logic]], to denote the [[antecedent (logic)|antecedent]] of a [[proposition]]; thus in the proposition "If ''P'', then ''Q''", ''P'' denotes the hypothesis (or antecedent); ''Q'' can be called a [[consequent]]. ''P'' is the [[:wikt:assumption|assumption]] in a (possibly [[Counterfactual conditional|counterfactual]]) ''[[wikt:what if|What If]]'' question. The adjective ''hypothetical'', meaning "having the nature of a hypothesis", or "being assumed to exist as an immediate consequence of a hypothesis", can refer to any of these meanings of the term "hypothesis".

==Uses==
In its ancient usage, ''[[Hypothesis (drama)|hypothesis]]'' referred to a summary of the [[Plot (narrative)|plot]] of a [[Theatre of ancient Greece|classical drama]]. The English word ''hypothesis'' comes from the [[ancient Greek]] word [[wikt:ὑπόθεσις|ὑπόθεσις]] {{lang|hrc|hypothesis}} whose literal or etymological sense is "putting or placing under" and hence in extended use has many other meanings including "supposition".<ref name="HilbornMangel1997">{{cite book |last1=Hilborn |first1=Ray |last2=Mangel |first2=Marc |title=The ecological detective: confronting models with data |url=https://books.google.com/books?id=katmvQDi8PMC&pg=PA24 |access-date=22 August 2011 |year=1997 |publisher=Princeton University Press |isbn=978-0-691-03497-3 |page=24}}</ref><ref>''[[wikt:supposition|Supposition]]'' is itself a Latinate analogue of ''hypothesis'' as both are compound words constructed from words meaning respectively "under, below" and "place, placing, putting" in either language, Latin or Greek.</ref><ref>{{OEtymD|hypothesis}}</ref><ref>{{LSJ|u(po/qesis|ὑπόθεσις|ref}}.</ref>

In [[Plato]]'s ''[[Meno]]'' (86e–87b), [[Socrates]] dissects [[virtue]] with a method used by mathematicians,<ref>
[[Wilbur Knorr|Wilbur R. Knorr]], "Construction as existence proof in ancient geometry", p. 125, as selected by Jean Christianidis (ed.), ''Classics in the history of Greek mathematics'', Kluwer.</ref> that of "investigating from a hypothesis".<ref> [[Gregory Vlastos]], Myles Burnyeat (1994) ''Socratic studies'', Cambridge {{ISBN|0-521-44735-6}}, p. 1 </ref> In this sense, 'hypothesis' refers to a clever idea or to a convenient mathematical approach that simplifies cumbersome [[calculation]]s.<ref>"Neutral hypotheses, those of which the subject matter can never be directly proved or disproved, are very numerous in all sciences." — [[Morris Raphael Cohen|Morris Cohen]] and  [[Ernest Nagel]] (1934) ''An introduction to logic and scientific method'' p. 375. New York: Harcourt, Brace, and Company.</ref> [[Robert Bellarmine|Cardinal Bellarmine]] gave a famous example of this usage in the warning issued to [[Galileo Galilei|Galileo]] in the early 17th century: that he must not treat the motion of the Earth as a reality, but merely as a hypothesis.<ref>"Bellarmine (Ital. ''Bellarmino''), Roberto Francesco Romolo", ''Encyclopædia Britannica'', Eleventh Edition.: 'Bellarmine did not proscribe the Copernican system ... all he claimed was that it should be presented as a hypothesis until it should receive scientific demonstration.' {{EB1911|wstitle=Hypothesis|volume=14|page=208}}</ref>

In common usage in the 21st century, a ''hypothesis'' refers to a provisional idea whose merit requires evaluation. For proper evaluation, the framer of a hypothesis needs to define specifics in operational terms. A hypothesis requires more work by the researcher in order to either confirm or disprove it. In due course, a confirmed hypothesis may become part of a theory or occasionally may grow to become a theory itself. Normally, scientific hypotheses have the form of a [[mathematical model]].<ref>Crease, Robert P.  (2008) ''The Great Equations'' {{ISBN|978-0-393-06204-5}},  p.112 lists the [[conservation of energy]] as an example of accounting a [[constant of motion]]. Hypothesized by [[Nicolas Léonard Sadi Carnot|Sadi Carnot]], truth demonstrated by [[James Prescott Joule]], proven by [[Emmy Noether]].</ref> Sometimes, but not always, one can also formulate them as [[existential quantification|existential statements]], stating that some particular instance of the phenomenon under examination has some characteristic and causal explanations, which have the general form of [[Universal quantification|universal statements]], stating that every instance of the phenomenon has a particular characteristic.

In entrepreneurial setting, a hypothesis is used to formulate provisional ideas about the attributes of products or business models. The formulated hypothesis is then evaluated, where the hypothesis is proven to be either "true" or "false" through a [[Authentication|verifiability]]- or [[falsifiability]]-oriented [[experiment]].<ref>{{Cite journal |url=https://hbr.org/2013/05/why-the-lean-start-up-changes-everything |title=Harvard Business Review (2013) "Why Lean Startup Changes Everything" |journal=Harvard Business Review |date=May 2013 |access-date=2015-07-16 |archive-date=2021-10-28 |archive-url=https://web.archive.org/web/20211028155310/https://hbr.org/2013/05/why-the-lean-start-up-changes-everything |url-status=live |last1=Blank |first1=Steve }}</ref><ref>{{Cite web |url=http://leanstartup.pbworks.com/w/page/65946049/Intro%20to%20Lean%20Startup |title=Lean Startup Circle "What is Lean Startup?" |access-date=2015-07-16 |archive-date=2015-07-16 |archive-url=https://web.archive.org/web/20150716103239/http://leanstartup.pbworks.com/w/page/65946049/Intro%20to%20Lean%20Startup |url-status=live }}</ref>

Any useful hypothesis will enable [[prediction]]s by [[reasoning]] (including [[deductive reasoning]]). It might predict the outcome of an [[experiment]] in a [[laboratory]] setting or the observation of a phenomenon in [[nature]]. The prediction may also invoke statistics and only talk about probabilities. [[Karl Popper]], following others, has argued that a hypothesis must be [[Falsifiability|falsifiable]], and that one cannot regard a proposition or theory as scientific if it does not admit the possibility of being shown to be false. Other philosophers of science have rejected the criterion of falsifiability or supplemented it with other criteria, such as verifiability (e.g., [[verificationism]]) or coherence (e.g., [[confirmation holism]]). The [[scientific method]] involves experimentation to test the ability of some hypothesis to adequately answer the question under investigation. In contrast, unfettered observation is not as likely to raise unexplained issues or open questions in science, as would the formulation of a [[crucial experiment]] to test the hypothesis. A [[thought experiment]] might also be used to test the hypothesis.

In framing a hypothesis, the investigator must not currently know the outcome of a test or that it remains reasonably under continuing investigation. Only in such cases does the experiment, test or study potentially increase the probability of showing the truth of a hypothesis.<ref name="Popper1959">{{harvnb|Popper|1959}}</ref>{{rp|pp17,49–50}} If the researcher already knows the outcome, it counts as a "consequence" — and the researcher should have already considered this while formulating the hypothesis. If one cannot assess the predictions by observation or by [[experience]], the hypothesis needs to be tested by others providing observations. For example, a new technology or theory might make the necessary experiments feasible.

==Scientific hypothesis==
A trial solution to a problem is commonly referred to as a hypothesis{{mdash}}or, often, as an "[[educated guess]]"<ref>
"When it is not clear under which law of nature an effect or class of effect belongs, we try to fill this gap by means of a guess. Such guesses have been given the name ''conjectures'' or ''hypotheses''.", [[Hans Christian Ørsted]](1811) "First Introduction to General Physics" ¶18. ''Selected Scientific Works of Hans Christian Ørsted'', {{ISBN|0-691-04334-5}} p.297</ref><ref name=Feynman >"In general we look for a new law by the following process. First we guess it. ...", —[[Richard Feynman]] (1965) ''[[The Character of Physical Law]]'' p.156</ref>{{mdash}}because it provides a suggested outcome based on the evidence. However, some scientists reject the term "educated guess" as incorrect. Experimenters may test and reject several hypotheses before solving the problem.

According to Schick and Vaughn,<ref>{{cite book |author1=Schick, Theodore |author-link1=Theodore Schick |author2=Vaughn, Lewis |title=How to think about weird things: critical thinking for a New Age |publisher=McGraw-Hill Higher Education |location=Boston |year=2002 |isbn=0-7674-2048-9}}</ref> researchers weighing up alternative hypotheses may take into consideration:
* [[Testability]] (compare [[falsifiability]] as discussed above)
* Parsimony (as in the application of "[[Occam's razor]]", discouraging the postulation of excessive numbers of [[wikt:entity|entities]])
* Scope – the apparent applicability of the hypothesis to multiple known [[Phenomenon|phenomena]]
* Fruitfulness – the prospect that the hypothesis may explain further phenomena in the future
* Conservatism – the degree of "fit" with existing recognized knowledge-systems.

==Working hypothesis==
{{main|Working hypothesis}}
A [[working hypothesis]] is a hypothesis that is provisionally accepted as a basis for further research<ref>''Oxford Dictionary of Sports Science & Medicine''. [http://www.answers.com/topic/working-hypothesis Eprint] {{Webarchive|url=https://web.archive.org/web/20111127203204/http://www.answers.com/topic/working-hypothesis |date=2011-11-27 }} via Answers.com.</ref> in the hope that a tenable theory will be produced, even if the hypothesis ultimately fails.<ref name=Century>See in "hypothesis", ''[[Century Dictionary]] Supplement'', v. 1, 1909, New York: [[The Century Company]]. Reprinted, [https://archive.org/stream/centurydictionar11whituoft#page/616/mode/1up v. 11, p. 616] (via ''Internet Archive'') of the ''Century Dictionary and Cyclopedia'', 1911. {{quote|'''hypothesis''' [...]—'''Working hypothesis''', a hypothesis suggested or supported in some measure by features of observed facts, from which consequences may be deduced which can be tested by experiment and special observations, and which it is proposed to subject to an extended course of such investigation, with the hope that, even should the hypothesis thus be overthrown, such research may lead to a tenable theory.}}</ref>
Like all hypotheses, a working hypothesis is constructed as a statement of expectations, which can be linked to the [[exploratory research]] purpose in empirical investigation. Working hypotheses are often used as a [[conceptual framework]] in qualitative research.<ref>
{{cite journal
 |author= [[Patricia M. Shields]], Hassan Tajalli
 |year=2006
 |title=Intermediate Theory: The Missing Link in Successful Student Scholarship
 |url=http://ecommons.txstate.edu/polsfacp/39/
 |journal=Journal of Public Affairs Education
 |volume=12 |issue=3 |pages=313–334
|doi=10.1080/15236803.2006.12001438
 |s2cid=141201197
 }}</ref><ref>
{{cite book
 |author= [[Patricia M. Shields]]
 |year=1998
 |chapter=Pragmatism As a Philosophy of Science: A Tool For Public Administration
 |url=http://ecommons.txstate.edu/polsfacp/33/
 |editor=Jay D. White
 |title=Research in Public Administration
 |volume=4 |pages=195–225 [211]
 |isbn=1-55938-888-9
}}</ref>

The provisional nature of working hypotheses makes them useful as an organizing device in applied research. Here they act like a useful guide to address problems that are still in a formative phase.<ref>[[Patricia M. Shields]] and Nandhini Rangarajan. 2013. [https://books.google.com/books?id=tVYbAgAAQBAJ  ''A Playbook for Research Methods: Integrating Conceptual Frameworks and Project Management'']{{Dead link|date=January 2023 |bot=InternetArchiveBot |fix-attempted=yes }}. Stillwater, OK: New Forums Press. pp. 109–157</ref>

In recent years, philosophers of science have tried to integrate the various approaches to evaluating hypotheses, and the scientific method in general, to form a more complete system that integrates the individual concerns of each approach. Notably, [[Imre Lakatos]] and [[Paul Feyerabend]], Karl Popper's colleague and student, respectively, have produced novel attempts at such a synthesis.

==Hypotheses, concepts and measurement==
[[Concept]]s in Hempel's [[deductive-nomological model]] play a key role in the development and testing of hypotheses. Most formal hypotheses connect concepts by specifying the expected relationships between [[proposition]]s. When a set of hypotheses are grouped together, they become a type of [[conceptual framework]]. When a [[conceptual framework]] is complex and incorporates causality or explanation, it is generally referred to as a theory. According to noted philosopher of science [[Carl Gustav Hempel]],
:An adequate empirical interpretation turns a theoretical system into a testable theory: The hypothesis whose constituent terms have been interpreted become capable of test by reference to observable phenomena. Frequently the interpreted hypothesis will be derivative hypotheses of the theory; but their confirmation or disconfirmation by empirical data will then immediately strengthen or weaken also the primitive hypotheses from which they were derived.<ref name=Hempel>{{cite book|last=Hempel|first=C. G.|title=Fundamentals of Concept Formation in Empirical Science|location=Chicago|publisher=University of Chicago Press|year=1952}}</ref>{{rp|36}}

Hempel provides a useful metaphor that describes the relationship between a [[conceptual framework]] and the framework as it is observed and perhaps tested (interpreted framework).  "The whole system floats, as it were, above the plane of observation and is anchored to it by rules of interpretation. These might be viewed as strings which are not part of the network but link certain points of the latter with specific places in the plane of observation. By virtue of those interpretative connections, the network can function as a scientific theory."<ref name=Hempel />{{rp|36}} Hypotheses with concepts anchored in the plane of observation are ready to be tested. In "actual scientific practice the process of framing a theoretical structure and of interpreting it are not always sharply separated, since the intended interpretation usually guides the construction of the theoretician".<ref name=Hempel />{{rp|33}} It is, however, "possible and indeed desirable, for the purposes of logical clarification, to separate the two steps conceptually".<ref name=Hempel />{{rp|33}}

===Statistical hypothesis testing===
{{Main|Statistical hypothesis testing}}
When a possible [[correlation]] or similar relation between phenomena is investigated, such as whether a proposed remedy is effective in treating a disease, the hypothesis that a relation exists cannot be examined the same way one might examine a proposed new law of nature. In such an investigation, if the tested remedy shows no effect in a few cases, these do not necessarily falsify the hypothesis. Instead, [[statistical test]]s are used to determine how likely it is that the overall effect would be observed if the hypothesized relation does not exist. If that likelihood is sufficiently small (e.g., less than 1%), the existence of a relation may be assumed. Otherwise, any observed effect may be due to pure chance.

In statistical hypothesis testing, two hypotheses are compared. These are called the [[null hypothesis]] and the [[alternative hypothesis]]. The null hypothesis is the hypothesis that states that there is no relation between the phenomena whose relation is under investigation, or at least not of the form given by the alternative hypothesis. The alternative hypothesis, as the name suggests, is the alternative to the null hypothesis: it states that there ''is'' some kind of relation. The alternative hypothesis may take several forms, depending on the nature of the hypothesized relation; in particular, it can be two-sided (for example: there is ''some'' effect, in a yet unknown direction) or one-sided (the direction of the hypothesized relation, positive or negative, is fixed in advance).<ref>[https://books.google.com/books?id=v-walRnRxWQC&dq=statistical+hypothesis+medical&pg=PA168 Altman. DG., ''Practical Statistics for Medical Research'', CRC Press, 1990, Section 8.5],</ref>

Conventional significance levels for testing hypotheses (acceptable probabilities of wrongly rejecting a true null hypothesis) are .10, .05, and .01. The significance level for deciding whether the null hypothesis is rejected and the alternative hypothesis is accepted must be determined in advance, before the observations are collected or inspected. If these criteria are determined later, when the data to be tested are already known, the test is invalid.<ref name="Mellenbergh, 2008">Mellenbergh, G.J.(2008). Chapter 8: Research designs: Testing of research hypotheses. In [[H.J. Adèr]] & [[Gideon J. Mellenbergh|G.J. Mellenbergh]] (eds.) (with contributions by D.J. Hand), Advising on Research Methods: A consultant's companion (pp. 183–209). Huizen, The Netherlands: Johannes van Kessel Publishing</ref>

The above procedure is actually dependent on the number of the participants (units or [[sample size]]) that are included in the study. For instance, to avoid having the sample size be too small to reject a null hypothesis, it is recommended that one specify a sufficient sample size from the beginning. It is advisable to define a small, medium and large effect size for each of a number of important statistical tests which are used to test the hypotheses.<ref>[https://books.google.com/books?id=v-walRnRxWQC&dq=statistical+hypothesis+medical&pg=PA168 Altman. DG., ''Practical Statistics for Medical Research'', CRC Press, 1990, Section 15.3],</ref>

==Honours==
[[Mount Hypothesis]] in [[Antarctica]] is named in appreciation of the role of hypothesis in scientific research.

==List==
{{main category|Hypotheses}}
Several hypotheses have been put forth, in different subject areas:
*Astronomical hypotheses
*Authorship debates
*Biological hypotheses
*Documentary hypothesis
*Hypothetical documents
*Hypothetical impact events
*Hypothetical laws
*Linguistic theories and hypotheses
*Meteorological hypotheses
*Hypothetical objects
*Origin hypotheses of ethnic groups
*Hypothetical processes
*Hypothetical spacecraft
*Statistical hypothesis testing
*Hypothetical technology

==See also==
{{Wikisource1911Enc|Hypothesis}}
{{col div|colwidth=30em}}
* [[Axiom]]
* [[Bold hypothesis]]
* [[Case study]]
* [[Conjecture]]
* [[Explanandum]]
* [[Hypothesis theory]] – a research area in cognitive psychology
* [[Hypothetical question]]
* [[Logical positivism]]
* [[Operationalization]]
* ''[[Philosophiae Naturalis Principia Mathematica]]'' – for Newton's position on hypotheses
* [[Reductionism]]
* [[Research design]]
* [[Sociology of scientific knowledge]]
* [[Theorem#Hypothesis]]
* [[Thesis statement]]
{{colend}}

==References==
{{reflist|35em}}

==Bibliography==
* {{Citation|year=1959 |last= Popper |first= Karl R. | author-link= Karl Popper | title= [[The Logic of Scientific Discovery]]  }} 1934, 1959.

==External links==
* {{Wiktionary-inline}}
* {{Wikiversity-inline}}
* {{Commonscat-inline|Hypotheses}}
* [http://undsci.berkeley.edu/article/howscienceworks_01 "How science works"], ''Understanding Science'' by the University of California Museum of Paleontology.

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[[Category:Hypotheses| ]]
[[Category:Philosophy of science]]
[[Category:Scientific method]]
[[Category:Guessing]]