Hypothesis vs. Theory

A hypothesis is either a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena. In science, a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors. A theory is always backed by evidence; a hypothesis is only a suggested possible outcome, and is testable and falsifiable.

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Definition A suggested explanation for an observable phenomenon or prediction of a possible causal correlation among multiple phenomena. In science, a theory is a well-substantiated, unifying explanation for a set of verified, proven hypotheses.
Based on Suggestion, possibility, projection or prediction, but the result is uncertain. Certainty, evidence, verification, repeated testing.
Testable Yes Yes
Falsifiable Yes Yes
Is well substantiated No Yes
Data Usually based on very limited data Based on a very wide set of data tested under various circumstances.
Instance Specific: Hypothesis is usually based on a very specific observation and is limited to that instance. General: A theory is the establishment of a general principle through multiple tests and experiments, and this principle may apply to various specific instances.

edit Examples of Theory and Hypothesis

"No amount of experimentation can ever prove me right; a single experiment can prove me wrong." —Albert Einstein

Theory: Einstein's theory of relativity is a theory because it has been tested and verified innumerable times, with results consistently verifying Einstein's conclusion. However, simply because Einstein's conclusion has become a theory does not mean testing of this theory has stopped; all science is ongoing. See also the Big Bang theory, germ theory, and climate change.

Hypothesis: One might think that a prisoner who learns a work skill while in prison will be less likely to commit a crime when released. This is a hypothesis, an "educated guess." The scientific method can be used to test this hypothesis, to either prove it is false or prove that it warrants further study. (Note: Simply because a hypothesis is not found to be false does not mean it is true all or even most of the time. If it is consistently true after considerable time and research, it may be on its way to becoming a theory.)

This video further explains the difference between a theory and a hypothesis:

edit Common Misconception

People often tend to say "theory" when what they're actually talking about is a hypothesis. For instance, "Migraines are caused by drinking coffee after 2 p.m. — well, it's just a theory, not a rule."

This is actually a logically reasoned proposal based on an observation — say 2 instances of drinking coffee after 2 p.m. caused a migraine — but even if this were true, the migraine could have actually been caused by some other factors.

Because this observation is merely a reasoned possibility, it is testable and can be falsified — which makes it a hypothesis, not a theory.

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Comments: Hypothesis vs Theory

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Anonymous comments (2)

October 11, 2013, 1:11pm

"In science, a theory is a well-substantiated, unifying explanation for a set of verified, proven hypotheses."

But there's no such thing as "proven hypotheses". Hypotheses can be tested/falsified, they can't be "proven". That's just not how science works. Logical deductions based on axioms can be proven, but not scientific hypotheses.

On top of that I find it somewhat strange to claim that a theory doesn't have to be testable, if it's built up from hypotheses, which DO have to be testable...

— 80.✗.✗.139

May 6, 2014, 11:45pm

"Evolution is a theory, not a fact, regarding the origin of living things."
this statement is poorly formed because it implies that a thing is a theory until it gets proven and then it is somehow promoted to fact. this is just a misunderstanding of what the words mean, and of how science progresses generally.

to say that a theory is inherently dubious because "it isn't a fact" is pretty much a meaningless statement. no expression which qualified as a mere fact could do a very good job of explaining the complicated process by which species have arisen on Earth over the last billion years. in fact, if you claimed that you could come up with such a single fact, now THAT would be dubious!

everything we observe in nature supports the theory of evolution, and nothing we observe contradicts it. when you can say this about a theory, it's a pretty fair bet that the theory is correct.

— 71.✗.✗.151


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