• Czech: hypotéza ,
• Finnish: hypoteesi
• German: Hypothese
• Portuguese: hipótese
• Spanish: hipótesis

• Czech: hypotéza, domněnka
• Finnish: hypoteesi, olettamus, otaksuma
• German: Hypothese
• Portuguese: hipótese
• Spanish: hipótesis

• ttbc Catalan: hipòtesi
• ttbc Chinese: 假说 (jiǎ shuō)
• ttbc Dutch: hypothese
• ttbc French: hypothèse
• ttbc Icelandic: tilgáta , skýringartilgáta , skýringartilraun
• ttbc Italian: Ipotesi
• ttbc Japanese: 仮説 (kesetsu)
• ttbc Norwegian: hypotese
• ttbc Persian: فرضیه (farziyeh), نگره (negareh)
• ttbc Romanian: ipoteză
• ttbc Swedish: hypotes
• ttbc Turkish: hipotez

A hypothesis (from Greek ) consists either of a suggested explanation for a phenomenon or of a reasoned proposal suggesting a possible correlation between multiple phenomena. The term derives from the Greek, hypotithenai meaning "to put under" or "to suppose." The scientific method requires that one can test a scientific hypothesis. Scientists generally base such hypotheses on previous observations or on extensions of scientific theories. Even though the words "hypothesis" and "theory" are often used synonymously in common and informal usage, a scientific hypothesis is not the same as a scientific theory.

In early usage, scholars often referred to a clever idea or to a convenient mathematical approach that simplified cumbersome calculations as a hypothesis; when used this way, the word did not necessarily have any specific meaning. Cardinal Bellarmine gave a famous example of the older sense of the word in the warning issued to Galileo in the early 17th century: that he must not treat the motion of the Earth as a reality, but merely as a hypothesis.

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. Sometimes, but not always, one can also formulate them as 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 statements, stating that every instance of the phenomenon has a particular characteristic.

Any useful hypothesis will enable predictions 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 falsifiable, and that one cannot regard a proposition or theory as scientific if it does not admit the possibility of being shown false. To meet this additional criterion, it must at least in principle be possible to make an observation that would disprove the proposition as false, even if one has not actually (yet) made that observation. A falsifiable hypothesis can greatly simplify the process of testing to determine whether the hypothesis has instances in which it is false. The scientific method involves experimentation on the basis of falsifiable hypotheses in order to answer questions and explore observations.

In framing a hypothesis, the investigator must not currently know the outcome of a potentially falsifying 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. 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 classes as not yet useful, and must wait for others who might come afterward to make possible the needed observations. For example, a new technology or theory might make the necessary experiments feasible.

In the United States of America, teachers of science in primary schools have often simplified the meaning of the term "hypothesis" by describing a hypothesis as "an educated guess". Overemphasizing this aspect fails to convey the explanatory or predictive quality of scientific hypotheses. To define a hypothesis as "an educated guess" resembles describing a tricycle as a "vehicle with three". The definition omits the concept's most important and characteristic feature: the purpose of hypotheses. People generate hypotheses as early attempts to explain patterns observed in nature or to predict the outcomes of experiments. For example, in science, one could correctly call the following statement a hypothesis: identical twins can have different personalities because the environment influences personality. In contrast, although one might have informed one's self about the qualifications of various political candidates, making an educated guess about the outcome of an election would not qualify as a scientific hypothesis: the guess lacks an underpinning generic explanation.

Evaluating hypotheses

The hypothetico-deductive method (also known as the method of "conjectures and refutations", cf Karl Popper) demands falsifiable hypotheses, framed in such a manner that the scientific community can prove them false (usually by observation). Strictly speaking, a hypothesis cannot be "confirmed", because there is always the possibility that a future experiment will show that it is false. Hence, failing to falsify a hypothesis does not prove that hypothesis: it remains provisional. However, a hypothesis that has been rigorously tested and not falsified can form a reasonable basis for action, i.e., we can act as if it is true, until such time as it is falsified.

For example: someone who enters a new country and observes only white sheep might form the hypothesis that all sheep in that country are white. It can be considered a hypothesis, as it is falsifiable. Anyone could falsify the hypothesis by observing several black sheep. Provided that the experimental uncertainties remain small (for example, provided that one can fairly reliably distinguish the observed black sheep from (say) a goat), and provided that the experimenter has correctly interpreted the statement of the hypothesis (for example, does the meaning of "sheep" include rams?), finding a black sheep falsifies the "white sheep only" hypothesis. However, one cannot consider failure to find black sheep as proof that no black sheep exist.

Scientific hypothesis

People refer to a trial solution to a problem as a hypothesis — often called an "educated guess" — because it provides a suggested solution based on the evidence. Experimenters may test and reject several hypotheses before solving the problem.

According to Schick and Vaughn, researchers weighing up alternative hypotheses may take into consideration:

• Testability (compare falsifiability as discussed above)
• Simplicity (as in the application of "Occam's Razor", discouraging the postulation of excessive numbers of entities)
• Scope - the apparent application of the hypothesis to multiple cases of phenomena
• Fruitfulness - the prospect that a hypothesis may explain further phenomena in the future
• Conservatism - the degree of "fit" with existing recognized knowledge-systems

See also

• Case study
• Ecological fallacy
• Hypothesis Theory, a research area in Cognitive Psychology
• Learning
• Logic
• Null hypothesis
• Null Hypothesis - The Journal of Unlikely Science
• Philosophiae Naturalis Principia Mathematica for Newton's position on hypotheses
• Reductionism
• Research design
• Scientific method
• Thought experiment

References

External links

• Research and Evaluation Glossary

a priori principle, affirmation, apriorism, assertion, assumed position, assumption, axiom, basis, categorical proposition, conjecture, data, first principles, foundation, ground, guesswork, hypothesis ad hoc, inference, lemma, major premise, minor premise, philosopheme, philosophical proposition, position, postulate, postulation, postulatum, premise, premiss, presumption, presupposal, presupposition, proposition, propositional function, set of postulates, speculation, statement, sumption, supposal, supposing, supposition, surmise, theorem, theory, thesis, truth table, truth-function, truth-value, working hypothesis