A hypothesis (plural hypotheses) is a proposed explanation
for a phenomenon
. For a hypothesis to be a scientific hypothesis, the scientific method
requires that one can test
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 synonymously, a scientific hypothesis is not the same as a scientific theory
. A working hypothesis
is a provisionally accepted hypothesis proposed for further research
in a process beginning with an educated guess or thought.
A different meaning of the term ''hypothesis'' is used in formal logic
, to denote the 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 assumption
in a (possibly counterfactual
) ''What If
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".
In its ancient usage, ''hypothesis
'' referred to a summary of the plot
of a classical drama
. The English word ''hypothesis'' comes from the ancient Greek
whose literal or etymological sense is "putting or placing under" and hence in extended use has many other meanings including "supposition".
'' (86e–87b), Socrates
with a method used by mathematicians, that of "investigating from a hypothesis." In this sense, 'hypothesis' refers to a clever idea or to a convenient mathematical approach that simplifies cumbersome calculation
s. Cardinal Bellarmine
gave a famous example of this usage 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.
In entrepreneurial science, a hypothesis is used to formulate provisional ideas within a business setting. The formulated hypothesis is then evaluated where either the hypothesis is proven to be "true" or "false" through a verifiability
- or falsifiability
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 falsifiable
, and that one cannot regard a proposition or theory as scientific if it does not admit the possibility of being shown 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 as well.
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.
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.
People refer to a trial solution to a problem as a hypothesis, often called an "educated guess
["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]
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, researchers weighing up alternative hypotheses may take into consideration:
as discussed above)
* Parsimony (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.
A working hypothesis
is a hypothesis that is provisionally accepted as a basis for further research in the hope that a tenable theory will be produced, even if the hypothesis ultimately fails.
[See in "hypothesis", ''Century Dictionary Supplement'', v. 1, 1909, New York: The Century Company. Reprinted]
v. 11, p. 616
(via ''Internet Archive'') of the ''Century Dictionary and Cyclopedia'', 1911.
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.
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.
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
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."
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." 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."
[Hempel, C. G. (1952). Fundamentals of concept formation in empirical science. Chicago, Illinois: The University of Chicago Press, p. 33.]
It is, however, "possible and indeed desirable, for the purposes of logical clarification, to separate the two steps conceptually."
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).
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.
[Mellenbergh, G.J.(2008). Chapter 8: Research designs: Testing of research hypotheses. In H.J. Adèr & 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]
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.Altman. DG., ''Practical Statistics for Medical Research'', CRC Press, 1990, Section 15.3
Mount Hypothesis in Antarctica is named in appreciation of the role of hypothesis in scientific research.
* Bold hypothesis
* Case study
* Hypothesis theory – a research area in cognitive psychology
* Hypothetical question
* Logical positivism
* ''Philosophiae Naturalis Principia Mathematica'' – for Newton's position on hypotheses
* Research design
* Sociology of scientific knowledge
* Thesis statement
* 1934, 1959.
"How science works"
''Understanding Science'' by the University of California Museum of Paleontology.
Category:Philosophy of science